I do most of my thru-drilling before I turn the plug, except on anything like a swimmer for example that may need an offset hole!
Someone here posted a picture of a jig they made....it is simply made of three pieces of wood (I used 1 by 4 pine board) take 2 pieces and make a corner out of them, more or less, and then just mount them on top of the third piece (maybe someone can post that pic again or do a search...it must be here somewhere. Then I just clamp it to the drill press table with two clamps after I have found the center and I drill all my pieces!
