Can I Remove Some Of The Fibers To Get Even Greater Detail In Pal Tiya Premium?

Yes you can. 

First make your initial 'rake-surfaced' "strength coat" onto your tinfoil armature/shape with Pal Tiya Premium. For your final detail coat, find a fine mesh strainer and sift out up to 50% of the fibers before mixing it with the water. This second coat will accept a lot more surface decoration, fine detail and texture. But be warned, this will make your surface slightly weaker, so maybe do this only where you want extreme detail. That initial base coat will give your sculpture the strength it needs.