Unless they have been replaced with something different, those screws should just be basic phillips screws...any smallish phillips-head screwdriver should do it. I don't know the technical size of the screws, and it really shouldn't matter so much. If they are problematic, I sometimes use a slightly larger phillips, which can give you a better grip.
If you've gotten to step 28, you should already have a screwdriver capable of dealing with those screws, so I get the idea from your question that there's something more to it than that...are they torx screws, or possibly are they stripped?