I presume you mean part 12-176. here's what you do, first you grow your fingers about 3 inches, then you strengthen then by tying weights to their tips. Others have had good success training MOWOGs.
Seriously, it is a picky job but they key seems to be a tool that pretty much all of us have made that is used to rest the clip in and then pull up onto the metal/trim. The top slides through the window slot. I had an old soft metal wrench that had come with some assembly kit years ago, someone else used the metal strap that would act to stop the brake bolts loosening. there are many options. BTW be careful I'm missing two-three clips in the door somewhere