Let me start with, I can not claim this as my own. I learned these tips from Chris (Bronco71) but thought I could pass them along.
The rear take down pivot pin can be a hassle sometimes when changing stocks or putting together. Here is a nice little tip. Use a #4-40 course tap, cut 3-4 coils off the spring, use a 4-40 set screw to seal it off. Nice and easy and pretty cheap. The tap cost me $8.40 and the set screws were $6.40 for 100 (only way I could find them. I used Fastenal for both.
Before: In the event you have never taken one apart the hole we are talking about is the tiny one on the right side of the rear of the lower receiver
Put some grease on the tap to catch the shavings.
Tap the receiver, straight and slow. I used WD40 with the tube to blow the shavings back out that the grease did not pick up.
Lube up and insert rear pivot pin, insert detent pin
Insert spring after cutting 3-4 coils
Thread the set screw in flush with the receiver and you are done.
No need to use Loc-Tite once the stock goes on there is no way it will back out.