As Ashley points out, "Prefer to add the shader effect to a whole layer, then put any objects you want to have that effect on that layer. This means the overhead of processing a shader only happens once." Thus, I control the tint and brightness of other layers independently (per layer basis) using the Tint effect applied on a layer.
Unlike the Tint mask, Tint affects only the tinted object/layer (and does not affect background objects/layers). As a further optimization, be sure to keep the option "Force own texture" of non masked layers (simply tinted layers) off.
Anyway, Ashley, it would be very useful, for situations like this, to have a plugin which composits/blends chosen images/sprites in real-time (per tick basis) and gives them readily available as a single image/sprite object. Thus, we could elminate the overhead of using the transitory invisible layer (as is the case with Paster plugin) and would have a more elegant overall solution.