The ONLY advice I will give is get some quality training from an aerobatics instructor and do exactly what he says.
Once you are cleared solo in the aeroplane and confident with the tail slide you may want to experiment with positive or negative (canopy down first) slides.
Don't try it on your own first time!
Even if you really botch a stall turn, you'll have to work very hard to tail slide it properly if you close the power.
Stik