Yaw Trim vs Roll Trim on Final

[Bazamataz]

When lining up for final I always seem to drift one direction or another, very slowly, finding it difficult to keep aligned with the runway despite keeping the nose exactly lined up with the end of the landing zone. I have always used Yaw trim to correct this (with variable results) but was thinking perhaps I should be using Roll Trim (which I have never used) instead.
All my practice flights have been with ZERO wind and NO munitions.
I understand the difference between the 2 types in theory (Rudder Trim Vs Aileron Trim) but in practice because the drift in is so slight it's difficult to tell if it's because I'm rolling or yawing.
I'm assuming this affect is the result of changes in Power, and Prop Torque, as I adjust my descent rate, not sure if I should be using Yaw trim or Roll Trim to counter prop Torque?
I also understand that if I had an uneven payload of munitions on the wings I'd need to use Roll Trim and if the drift was due to wind I'd need to use Rudder trim to keep the nose lined up, but none of these 2 factors are relevant here.
Which trim do you use when on final to keep you lined up?

[SharpeXB]

Being trimmed is fine but you’ll need your need your primary controls. It’s unlikely your plane will be lined up that perfectly to rely entirely on trimming your flight path. And yes changes in engine power will require corrections. 

[Bazamataz]

Thanks, I guess I shouldn't be focusing on trim too much but be using the stick to control the aircraft on final. Or rather, I should expect an appropriately trimmed aircraft to still need stick input, even when lined up, despite there being no wind/munitions effect.

[ZachariasX]

You don't fly your aircraft with the trim. You tim it for it going straight while you have your controls centered.

 

Regarding control:You trimmed the AC for landing configuration while in the circuit, you use stick inputs to fly her to the approach. When entering final, you only use rudder and elevator. You DON'T use ailerons unless for keeping her attitude, be it level or tilted towards the crosswind. In the final you don't steer anymore with the ailerons. It can be dangerous if you do.

[TP_Jacko]

The runways are  quite wide on landing. If you  have the power level right you would normally be on a nice glide slope. 

I only use the stick

[SharpeXB]

Pinned right above this thread. These are excellent.