Barry Brown, an effervescent jockey agent, pulls up to a barn in his van on the backstretch at Arlington International Racecourse.

Brown is trying to do another agent a favor, by getting a California jockey a mount in today's Arlington Million, but anyone listening to the fast talking New Yorker would be uncertain about exactly what he's doing.

The first person Brown sees at the barn is Mahmoud Fustok, the Saudi Arabian who is running Fijar Tango in the Million.

"Hey," Brown yells to Fustok, across a passenger inthe front seat and and through the window on the other side of the van. Fustok approaches the vehicle, smiling, and it is obvious that they know each other.

"Hey," Brown says again. "I got a bone to pick with you. When are you going to say hello to Georgie. Georgie rides all those horses for you over there in France, and you don't say hello to him?"

The handsome, tanned Fustok is taken aback, about to apologize for something he hasn't done.

"How can I say hello to him?" he says to Brown in a pleading tone. "I just got here. How can I say hello to him if he isn't here? Where is he that I can say hello?"

Brown isn't having any. "Well," he says, "just make sure you say hello to Georgie."

Fustok already has his rider--Angel Cordero--for Fijar Tango, who is the best horse from Europe in the Million, so Brown drives his passengers back to the racing secretary's office.

"A few years ago, I gave that guy a $20 horse in Florida," Brown says. "Who knows how much a guy like that might have bet on it? But all I know is that he's liked me ever since.

Many a horseman likes Brown at Arlington these days, not because of his high pressure personality, but because he represents Jorge (Georgie) Velasquez, the hottest rider on the grounds. Through last Wednesdays action, Velasquez had ridden 72 winners here, putting him atop the jockey standings, 11 victories ahead of Pat Day. Velasquez has been winning with more than 21% of his mounts, an excellent percentage, and his horses have earned almost $1.3million.

Brown, who has been booking horses for Velasquez since April and came here for the beginning of the season in late June, is the opposite of the soft-spoken jockey. The agent speaks loudly, whereas Velasquez, 42, just rides, reviving a career that seemed to have reached the end.

Before arriving at Arlington, Velasquez had ridden only 38 winners in almost six months in New York, and had become a forgotten man for the trainers there who used to entrust him with their best stakes horses.

Now, Velasquez frequently is offered rides on more than one horse in a race, and he and Brown must sort out the best mounts. Today, Velasquez rides Frosty the Snowman, who, at 8-1 is a dangerous horse in the Million, having run two strong races over the Arlington course in the last five weeks.

"Jorge is riding like a 19-year-old," trainer Jack Van Berg said recently.

Not only is Velasquez booting home winners, they are giving good value to the bettors who support him. The average payoo on a winning horse ridden by Velasquez has been $8.55, which is almost $2 more than a typical winner ridden by Day. For years, Day has been the most popular and successful jockey in the Midwest. Velasquez has been an Eastern rider for most of his 25-year career.

The son of a Panamanian butcher, Velasquez added a major accomplishment to his considerable career last Sunday when he rode Pappa's Fuzzbuster, a 4-year-old $5000 claiming horse, to victory in the second race here. That was the 6033rd victory for Velasquez and it moved him ahead of Johnny Longden on the list. Only three jockeys are ahead of Velasquez--Bill Soemaker, who will retire early next year with more than 8,800 winners; Laffit Pincay, who has about 7,260 wins; and Angel Cordero, who has more than 6,740.

Winning 600 races and then passing Longden, however, rank behind the Kentucky Derby that he won aboard Pleasant Colony in 1981 on Velasquez's personal list of achievments. Other highlights for him are a victory with Proud Truth in the 1985 Breeder's Cup Classic, his victory aboard Chris Evert in the match race against Miss Musket and Pincay at Hollywood Park in 1974 and early last, while riding at Santa Anita, he became only the fourth jockey to reach the $100 million mark in purse.

Velasquez took a giant step on the way to that plateau in 1985. Riding primarily for trainer Wayne Lukass, he won 57 stakes, still a record.

Velasquez and Vic Gilardi, his agent of more than 20 years, were riding high then, but their relationship was soon shattered, mainly because Lukas began using other riders.

There are two versions of the Lukas-Velasquez falling out. One is that Velasquez honored a commitment to ride Proud Truth in a stake when Lukas wanted him to ride one of his horses. The other, which comes from Velasquez, revolves around a defeat suffered by Lady' Secret in a race in which the jockey rode another horse.

"Jeff Lukas got real mad at me after that one." Velasquez said. "I can't even remember the filly that I rode, except that she was trained by Ben Perkins. Jeff said that I got Lady's Secret beat, but I sure wasn't trying to do that. I was just trying to win the race. If I wanted to get Lady's Secret beat, I would have pinned her against the fence, I would have been all over her, and I didn't do that."

Velasquez seemed to ricochet from one venue to another after Lukas quit using him. He spent 10 months in France, where his wife and children had difficulty with the cultural adjustment. He returned to New York and went out to California, where his new agent, Camilo Marin, got sick and died only a few months after his arrival.

Then he was back in New York, where this spring he hired Barry Brown.

To be continued.