I have to reiterate Keriks comment of "if it aint broke" so if things are working for you one way, dont mess with a good thing.
Michael for what its worth, if you continue doing the brush development, get a really large hake brush from jerrysartarama.com, for 7x17 negatives I use a 10" Mandalay Hake brush
only $10 and I usually buy two or three of them and dedicate them for negative development. tossing them as they get old and start falling apart.
given the size of 7x17 and (your) 12x20 negs one thing to consider looking into is getting a small 7.5 watt safelight and green filter and you could experiment with dev. by inspection.
Michael Smith has a very good article about it here:
after reading that article and just diving right in I found it to be pretty "easy" to learn.
good luck with it. Sounds like you are really on your way and doing well with it.