Depends on the problem 
CHGORAM was one of the hardest (as I’m sure @vijju123 can attest :)), and took quite a bit of pondering before even writing out the initial draft. Actually typing it up tends to be fairly quick, so let’s say about - 4 hours or so for CHGORAM?
Others are easier - according to my git logs, the documentation for CHEFDIL seems to have taken about 45 mins, which isn’t too bad I also actually did the “observation problem” approach first, and then tried to figure out why on earth it worked XD
BACREP was probably about 3 hours or so.
Cleaning up and refactoring the code to be readable is usually the quickest part, and the most fun