the factory pillars are pressed into place, atleast on the laminate stocks.
I actually had a brand new VLP laminate stock that they undersized the rear pillar hole, then split the stock when they pressed in the pillar. You could push it out with 1 finger. I had my local smith repair the crack by milling a slot across the stock and installing a metal brace into it, then epoxy it into place. He also installed a new pillar(epoxied into place this time).
I also drill small holes at different angles around the pillars to give the bedding compound some extra places to lock into. Like this:
Another good tip is to go to the hardware store and get some 2.5-3" long 1/4x28 bolts. Cut the head off them and screw them into the action before you bed to use them as a guide. It makes it alot easier to line up the holes. I also tape around the screws so it is a snug fit into the pillar, that way no compound gets into the inside of the pillar. Just remember to use your release agent on these also.
Oh, and Play-Doh works good for filling in the gaps in the action, but dont let it sit too long before you bed it cause the Play-Doh dries and cracks.
If you do a bedding job and it doesnt come out smooth when you pull it out (or there are areas that could use more bedding), just clean the releasing agent off the existing bedding and apply another layer, giving it a skim bed to fill in all the low spots. These low spots will also occur if you go overboard and use too much Pam cooking spray as the release agent.