doughboy, in regard to drifting speed, there are a couple of things you may want to consider. The faster you are drifting, the higher your baits will be in the water column so you need to weight them properly, when needed. Drifting too fast without weight and your baits will plane. Generaly speaking, the more ground you cover, the better your chances, however, you always want to be over good structure. Fishing a wreck out in the middle of nowhere and drifting 5 miles from it would probably not be too productive.
In regard to how much distance you should keep from someone else's slick, I stay a least 1 mile away. The oil on top attracts fish and trying to figure out the sink rate of your chum is impossible. There are currents, up-swellings, etc., happening below the surface so you only know what you can see.
F/V NIKKI ANN