Trainers can be very acrobatic, but they need to be setup for it. So the first thing to do is move the balance point back about 1/4" at a time. As you do this, the airplane will become much more sensitive to elevator, as well as the rudder. At the same time, you want to crank up the throw on both the rudder and ailerons. More power also helps, but often trainers can get better performance with just a propeller change. Usually increasing the diameter and lowering the pitch, or just lowering the pitch on the same diameter helps. Experiment with a half dozen sizes and pick the one that works best.

In my opinion, the LT-40 is one of the best trainers. Set-up for acro, it will do inside and outside loops, spins, snap-rolls, and inverted flying until the tank runs dry. Everything else is just a combination of these basic elements.