So I decided to not bother disassembling anything and just sprayed part of the inside.
There were two screws to remove the hard hat liner. I then taped up all the parts I didn't want sprayed and covered the entire helmet with a plastic bag to keep it clean.
After youtubing for a bit, I lightly sanded the inside with 220 grit and then wiped it down with mineral oil.
I only sprayed part of the helmet since this was my first attempt and I wanted to keep it simple. Ended up putting three coats on. You can see there was a decent size drip that formed during the last coat. I spent part of the time while it was drying slowly rotating it to fill a couple spots that didn't get covered as well. After I stopped, it eventually pooled up in the bottom and dripped to one side because I had it resting at an angle. I definitely over-sprayed on the last coat.
It's not perfect, however I can easily remove what I have if I wanted to fix the drip. Aside from the drip, it looks quite nice and smooth. For now, it's just fine and not visible to anyone when I'm wearing it. I'm probably going to spray the inside left and right side this weekend and also try and get some of the inner lip around the neck since that's the most visible part of the inside. Still needs a couple days of curing to get the smell out, but that's expected.