A big thing that helped me get more topspin on my 2 hander was switching my left hand grip from E to SW. The other thing was really letting it be a left handed forehand - letting my left hand really control the racquet. I still can't get as much spin as I can on my fh, but it's a good shot that has margin and will push people back when I'm hitting it well.
That said, I was on the wall yesterday. Hit 1 handers for a few minutes. It's really fun. Great feeling, lots of spin - very free and powerful. The problem is the wall doesn't dish out pace and spin like a real player.