Pick Slippage was a problem for me for a long time...even with drilling holes and emory boards....until I tried the Ultex Pick by Dunlop...it ROCKS! Not only that but I can't tear this pick up. A fender pick is shredded in a few days of use..I am on the same Ultex pick I got from a friend even though I have bought a few more bags...mainly to give away to friends.

As for hitting the right strings when strumming....I found trying to play some easy SRV songs helped. Cold Shot comes to mind....the rhythem is a pain at first but it helped me focus on hitting the right strings at the right time. Also, Cat Scratch Fever is a good one to help with that too.

Anyhow the above post is good too, cept I can only do so much "drilling" and then I gotta play. I try and find songs that empahsize what drills I am working on at the moment.