Re: Filling in neck holes and pot holes.
for the neck holes, you can use dowel glued in and then redrilled.
For the pot holes I'm not too sure since there's not a whole lot of surface area for the glue to hold onto strongly...it could create a pretty weak joint unless the dowel/piece of wood filling the hole is an ultra tight fit before gluing. Normal wood glue creates a bond that is usually stronger than the wood itself, provided the joint is an ultra tight fit. If it's anything but a tight fit, then the plug will not be properly bonded, and soon as you go to redrill a hole in it, it'll probably pop right through the old hole.