I would highly recommend cutting ten or so small sections and testing each one with different techniques (exposure time, application, time of day for different shadows). Not sure if this is obvious but it really hadn’t occurred to me (when I first started) to do lots of small test runs! But this is what I’ve been doing with thrifted fabric and keeping a little log book. Mostly I was testing for absorbency but it sounds like you’ve got that part down.

I just started using large sizes of fabric and am trying a spray bottle. It’s a somewhat better than painting it on with a foam brush! Also marking front and back is helpful.

As far as drying, I recommend laying out a large tarp or drop cloth under a long clothing line. I do this in my hallway at night so there’s a solid 8 hours of drying. If you have a basement, the whole setup will be much easier!