I cast a fair amount of PL, when the urge comes upon me. 38-55 and 41 LC HB are the main ones as the rifles bore is badly worn and the 41 starts it's journey at .385...ends at around .410. Lead works marvelous for this, but...I find lubing to be a pain. Can it really be as easy as hitting them with a spray bomb?
As a thread stealer (owning up anyhow ), latest 'casting only' rifle is a Marlin pump in 32-20. No real luck on it, it flings about 1 in 5 like a Monkey throwing poop....this with Bullet Barn 32-20 fodder at .312.
How much size difference does coating the bullets make? The Marlins are noted for having a generous bore. I'd rather go with a PL that obturates to the bore than the sizing ritual. Just saying...my time allotment isn't able to handle one more step in the process...running them through a sizer.
A buddy of mine put me on this "alternative coatings" idea a couple of years ago (thanks Auggie) so I have spent hours reading others experiences and more than a few hrs of my own testing.
The spray bomb paint thing has been mentioned a few times in some of my reading but it never really gained much traction. A couple of times it was mentioned that it "works" somewhat adequately in handgun length barrels, but even some handguns will lead up towards the end of the barrel. The problem is that the paint is very thin and brittle on a bullet and won't retain "coverage" for the full barrel travel, especially in a rifle barrel.
The PC coating, on the other hand, is very resilient and sticks like sh!t to a blanket if cooked properly. To answer your second question...PC coatings can be varied from around 1.5 thou and upwards with additional coatings. I have personally bumped up 230 gr hard cast .452 pistol bullets to .460 (3 coats) and then sized them to .459 and used them with outstanding results in a 45-70 that never before was a "tack driver" but will now shoot under 1 inch with them. The PCing may be just the ticket for your 32-20.
Timewise, PC'ing does have a learning curve that takes up a bit of time but, like all re-loading operations, once you get the hang of it, it doesn't use a lot of time at all. I can do 30 or 40 at a time in my setup and altho it takes 25 min or so to do a batch, I only use about 5 min to mix/coat and set on the tray for baking and once I hit the "20 min cook" dial I go do something else useful.
My "come away" with PCing is that it removes almost all the different alloy concerns and different messy lube concoctions (excepting BP cartridges, they still require a grease cookie or similar to soften the fowling) that each rifle seems to have their own preferences for...cast-PC-load and shoot.