I don\'t think brush on primer adheres quite as strongly as spray primer, or at least spray enamel which I believe actually etches into the metal a little.
But I don\'t have massive rub-off problems with the RMS primer. It\'ll rub off around the rim of the base a little and on high points like hair curls or something else that sticks out a lot or gets rubbed while I\'m painting, but I\'ve never had it peel off while applying paint. And if I do all my base coats first then I don\'t even get the handling rub off while painting except on the occasional very sharp/pointy part.
The RMS primer is not prone to peeling in general. I quite frequently scratch off a piece of dust or hair or whatever that got under the primer and it\'ll usually just scratch off that one tiny spot. One of the spray primers I tried, while it gave a really nice surface, would peel off until it got to an edge when I did that, and it also seemed kind of brittle, it cracked when I bent something into place and I\'ve never had that happen with any other kind of before.