I used brush/roll on Herculiner on the interior of a 16′ Lund that leaked approx 1 gallon in 4-5 hrs and it resulted in a dry interior. Some companies now have it available in lighter colors.
Also used the Rust-Oleum spray version on another old boat with a similar leak rate a year ago. When applied it looked suspect as the consistency is only slightly thicker than spray paint so applied 2 coats and 3+ to riveted areas. I’ve used the boat a few times and while I’m not confident it’s as dry as the first boat, it’s much better than it was – hard to tell after just 3-4 times cause of rain, spray, etc.
It’s not that difficult. Just clean the surface thoroughly and apply, both according to manufacturer’s instructions and make sure you apply it to the entire surface if you can. If you skip a spot hard to reach that’ll be the place that still leaks.
Herculiner runs $70-80 gallon, Rust-Oleum $7-8 a can. Either has a nice non-slip surface. The heat factor is obvious. Lighter colors = cooler.