metal shield is a silicone based enamel, if you use the professional range
it is better then automotive enamel, get the same build as two pak wont fade can be painted over if need be, its what I do for a living its used on heavy machinery, tough as nails, and you can use it on your clapped out tractor, but sounds like you know your paints, another advantage is it can be recoated in 10 minutes certainly suitable for that tractor
cheers

