my favorite hillbilly trick is to use a junk 3/8 in. extension wraped with electrical tape.  i wrap it a few times and test fit it before i fill the cavity with grease once the correct wrapping is found then fill it with grease and hammer away!

sometimes i use the clutch alignment tool as well.  the tip of it is the perfect size for obvious reasons.

also i have used anything insight and wraped paper towles or rags around it to fit.  i like the tape method i need to remember that one.

i have right now a wooden dowel that i sanded to fit about five years ago in my tool box.

I tried the tape trick but it kept sliding back. What I did find was that the 17mm bolts that bolt the rear tranny support to the frame are the perfect size.

I simply beat the crap out of it - replacing it anyway. The grease method has never worked for me..

I would pound the bolt in a little, remove it, and add a little more grease. As the pilot bearing moves forward you need to keep adding grease to keep the pressure from behind. Once its out you can clean all your grease out. I found that the back side of a 17 mm socket was perfect for getting the new bearing in.

Why mess with grease and crap and jerry-rigging when you can make this in 10 min and it will last forever.