trap -- I've not shot many grouse or woodcock, so others with more experience may chime in, but a 12ga 1 ounce load of #7 1/2s would be my choice if using a 12ga. As far as chokes for these birds... CYL, SK and IC would be good chokes to consider. Shoot a few patterns with each choke and your chosen load at the distance you expect to shoot your birds to find the combo that works best.
Here are a few of my pattern numbers to give you an idea of the kind of performance you might get.
Patterning results from a 12-gauge Browning Citori with 28" Invector-plus barrels using Briley flush chokes (patterns average of five, 30" post-shot scribed circle, yardage taped muzzle to target, and in-shell pellet count average of five).
30 YARDS
CYL / Win AA XL 1 oz #7.5 lead (344 pellets) / pattern 194 (56%)
SK / Win AA XL 1 oz #7.5 lead (344 pellets) / pattern 248 (72%)
IC / Win AA XL 1 oz #7.5 lead (344 pellets) / pattern 288 (84%)
Good luck.