To drain the block you don't need to remove freeze plugs, just take the 14 mm brass bolt/plug loose (circled in above picture) and the block will drain. This is a tapered brass plug that seals itself on the taper when it's tightened back up, so very little chance of creating a leak by taking it out and putting it back in. The bad part is access. It can be frustrating (especially on a 4wd) but not impossible to get it in/out (this is due to the terrible placement between the alternator and motor mount).
Here's a post I made a while back explaining how to flush:
http://www.toyotavantech.com/forum/s...=2735#post2735