Skidding on a suicide cog is a bad idea... you should have a front brake.

When I skid, I push back with my right leg and pull up with my left. I try to start the skid when my right foot is between 6 and 9 o'clock (about 7 o'clock is my happy spot). Probably not good advice, but while learning, I found myself looking at my left foot...almost staring it down and telling it not to move. Of course, I still have to lift my butt some and also tend to buck the back tire on occasion.

Personally, I'm still a fan of brakes.