You can google or do a search on Yahoo or any other search engine for terms like : blues lessons or blues scales or blues chords,
slide guitar lessons etc and find lots of links. A lot of the information is abstract to some extent but what blues is about is playing the major and minor penatonic scales for the most part. The most basic blues chords are E and Em and A7 and G. by playing these chords in a pattern like Em,A7,G you have the basic blues sound. To vary from that is basically you picking strings within each chord to get a sound you like. slow bending of the strings and poping the strings on the notes within the chords ad's your own touch to that. A old guy told me one time Blues aint about a style it's about a feel! Play what you feel! That makes it real to! Ive been playing a long time but am not real good at slide guitar and for me it's hard to get a feel for it but the procedure is simple it's all in the touch and feel . to some people it comes easy but for others you have to work at it. I use a glass slide right now but think I will change to a metal slide as they seam to have more friction and grab. Ive played with a lot of types of slides and a piece of copper pipe has more grab so you dont slip all over the strings making you sound sloppy. some good slide players go real fast but to start you might want to just cut some copper pipe as its soft and will grab the strings more so you dont slip all over the place till you get a feel for slide guitar. Then you can change over to a glass slide if you like. It takes time no matter what and I played for five years every day till I even got good at it! Some people are great quick. I taught my sister how to play the guitar and in six months she was great! Freaked me out that she was so good so quick but it was more natural for her I guess. Just remember each person is diferent and dont get frustrated and it will all fall in place in time.
Peace
Mojo Zap