i kinda cheated on the start slow part, and this might work for you too. for a month or two before i could solo, i knew what the scales looked like, so i sat down in front of the tv for a few hours watching movies or whatever was on and walked triplets up and down the guitar in key with whatever music was just on the tv. at first i had to concentrate on it, but after a while i just sort of did it without thinking about it. i got faster and faster without really thinking about it. i'll admit its not the best practice, but it worked great for me developing speed. try to use good technique from the start, hold your pick correctly and think a little bit about your alternate picking because if you don't, your right hand will have to catch up to the speed in your left hand (that happened to me) and it won't sound smooth.