sometimes the gird in hammer ?sn't small or big enough to support the door sisez
Doors always fit perfectly in their frames. Always, up to the nanometer. Oh, they don't? Nevermind then...
In other words, why care about a few lousy units if it's even natural? Plus, how often will a player notice the difference, anyway?
Back to the question, I'd say, check out
this tutorial. No need for origin brushes anymore.
As for the texturing, it may be a bit messy but you can give it a different offset and such using the texture application. I assume you are familiar with that tool?