We have lots of gravel here in Phoenix, much is pea sized but not smooth, so I don't know if we're on the same type of terrain. Sometimes it's a few inches deep, sometimes probably a good foot, depending on where the motors and ATV's have sprayed it. What we do is try to maintain speed as long as possible, floating over the surface, and trying to keep a loose, but firm grip on the handlebars. You don't want to make any sudden movements or attempt turns at this point, cuz you'll go down in an instant. In terms of speed, well, it depends on how fast I'm going in the first place. I'm not a race, I just want to live to ride tomorrow. If we're going at a good clip, I might just feather the brakes to take the edge off, so I'll have better control. Sometimes it's a mental thing, too. If it's a long stretch of gravel that I know I'm going to have to grind through anyway, I might knock down a few gears and prepare for that inevitability. Gravel can be scary, but the more you ride it, the more comfortable and confident you'll be. Have fun with it: we make it a contest to see who can get through the farthest.

One thing I didn't discuss--if the gravel is on a turn, better slow down well before the turn, at least until you're familiar with how it handles. Most of my elbow and knee scars come from skidding out of control on gravel in curves

Oh, one more thing: the kind of tire you use may make a difference. Here we use lots of big lugged tires to help get that float over the gravel, and then to dig through when we sink.

Hope this helps. Gravel was a nemisis for me for a long time.