I did mine on my F with POR15 from Frosts, its a one pack polyurethane paint that is many times better than Hammerite, nothing will touch it after it has cured. it is a thick coating paint and two coats make a wonderful job - coat the insides with wax oil.
Hoping to get mine back in soon.....I wore out a wire wheel in the angle grinder, course wire wool vinegar water followed by kure rust, painted with rustbuster 2 pack epoxy mastic all the box sections have been sprayed with a waxoyl type of stuff, to be fair the subframe was mainly light surface rust, the way I look at it is how much you want to throw at it, if you want to do it yourself and how long in the real world the rest of the car will last!