Reflex the ailerons UP instead of lowering them On many models (especially tapered wing with constant chord aileron or ailerons that do not extend into the center 1/3 of the wing) this works to help prevent dropping a wing in a stall and presents the belly of the wing as a big airbrake.
Wag the rudder and yo can bleed off a lot of speed.
A lower pitch prop will act as a better airbrake when you chop throttle.
Learn (at altitude) how to get "behind the power curve". Hold nose high and find minimum power to maintain altitude. Raise the nose a touch more and it should start sinking AND slow down. you can get in a condition that requires half throttle and you are flying essentially at minimum speed without stalling. A tiny reduction in power will cause it to descend. Control descent rate with throttle.