Re: trainers from Wal Mart
I agree that these won't hold a lot but they are so trim and soft they can be doubled up as a nice around the house option.
I will put two pairs on my baby some nights after a bath just to let his skin get a little air. At $7 for a three pack it is a nice, economical option for training at home. I am not training my 12 month old. I just like letting him go coverless every once in a while without the bulk of a fitted.
My best advice if you should decide to buy some, is to wash them any chance you get at first. They will shrink up nicely and fit better after multiple times through the washer and dryer.