Fertilization
 

Can you self-fertilize a paphiopedilum...?

Yes.

Almost all orchids can be selfed, and it is often done with rare color forms.

One of the very few exceptions I know of is Epidendrum melanoporphyreum. Woodstream Orchids was unable to breed it, till they got a second plant.

For some reason I can never self-fertilize my Phalaenopsis.

Is that called "pollinate?" I was thinking of fertilizer when I read your title.

Generations of selfing with no interference of other pollen (genetic materials) creates a species. On boundaries between species, you get various natural hybrids.

I found a good explaination how to do it on troymeyers.com/flasking and then look for article # 33. It is not really recommended because you need genetic diversity. Getting 2 plants from 2 different parents/breeders is much better.