I would like to create a power up that as I jump off a cliff I fall normally but if i Hold R1 I fall much slower, almost floating.

I can't figure out how to create it, I can't find a way to alter the characheters weight, only the object.

I have made powers ups already, I've created a light gun that also fires projectiles, I understand the controllinator part, just not how to slow descent.

Think of gravity as just a downwards vector, an upwards vector then will slow an object as it falls. You can create vectors in LBP using Movers.

Try these settings on a Mover: