Sounds to me like you are trying to just barely fill the space to be bedded. There is often a lot of room in a factory stock that needs filling for the job to be done right.
I usually mask off any areas I don't want resin on with good quality masking tape, use paste wax as a release agent on all exposed areas and metal parts, add floc or fibers to the resin before I add hardener and tap it on the bench to release as many air bubbles as possible, then mix the hardener in as smoothly as possible. I position the action screws in place so that all I have to do is tighten them as needed. I pour the mixture into the stock where I want the resin to be when I am done, let it spread by itself, then slowly put the action in place, and slowly tighten the action screws, making sure to wipe up all the excess resin that gets squeezed out as I tighten the screws. There are usually some small voids caused by bubbles, but no gaping canyons if I have done my part.