Practice, practice practice. You could buy a foamy which will let you practice all day long. Indoors and out. Try a good one from fancy foam like the yak By Gernot bruckman or a shockflyer. But the trick is letting you mind relax and naturally inputing whats needed without thinking about it. Also it is best to let someone effiecient in torque rolling trim out the plane. the right amount of right thrust and rudder trim is essential in cutting down the work load. When doing a perfectly verical torque roll you will notice very little control movement. But to keep this going you will have to be thinking ahead of the plane to make the right corrections.