I will cast on piles on occasion, but it's usually after I have vertical jigged the brushpile and found the edges. I throw a 1/32 or 1/16 oz jig and count it down. I try this until I find the depth the fish are in. I use a slow steady retrieve unless the fish are right at the bottom of the pile and then I use a slow pumping action while slow reeling, bumping it off bottom just out from the brushpile. On top of it I count down til I start hitting brush and shorten my count by 1 and slow reel across the top. I prefere vertical jigging with a pole, so someone should be able to help alot more than me. Crappiepappy has an article on "Vertical-casting" that I believe would help you. Use the seach engine and type in "vertical casting". He fishing alot of brushpiles and structure by casting. Hope this helps.
(I came back and put in the address to save you time.)
http://www.crappie.com/articles/crappiepappy.htm