oooh painting!!! I love to paint!
I think the chemical you are thinking of is TSP. If it isn't, it should be. It will even take the gloss off semi-gloss if you need to.
Always, always, always wash the wall before you paint. My very least favorite part about painting, but you gotta do it, smokers or no.
The very best part about painting Laura, is that if you don't like it, you can always repaint.
When I painted one of our rooms, I chose yellow, gold and white. My DH just about had a panic attack when he saw me toting in those colors. I sponged the colors, with the darker gold towards the bottom of the walls, fading to lighter the closer to the celing. I painted the celing yellow and white, sponged on. The effect is so wonderful and cheery! This room is an East facing window, and it gets zero direct sun, but because it's so cheery, it is never gloomy, ever.
Once it was done my DH complemented me, and said he would never doubt my color choices again. Or at least, he said he would never tell me he doubted them again...