To begin with, not having a training partner is an excuse! Get the heck away from the Smith machine...and find a power rack or bench that has safety racks. As far as Forced Reps: Why worry about doing weights that you need help on? Do the maximum weight you can do for the reps you want to get...isn't it about the weight YOU can lift and not what you can get help with? Try this technique on flat and incline barbell benches: Reduce the weight a bit, bring the bar down slowly and hold the bar at about 1 inch above touching your chest for a 2 second count, then press...your weight and reps will suffer, but your chest will feel it. I'm a firm believer that after a couple good warm ups, go for heavy weight and low reps...I'll even go down to singles. In fact, I use a true pyrimid...light weight/higher reps-heavy weight/low reps-moderate weight/moderate reps. As far as rest time, I don't like too much...30 seconds to a minute tops...and the latter if I've really gassed myself.