I've used Eastwood's stainless steel paint on cast manifolds, brushed on or sprayed (thinned with enamel reducer) and it's held up for 10 years. Sprayed some on some headers and it held up OK but did get some spots which were easily touched up with a brush. Always bead-blast first and wipe down with grease & wax remover. The initial baking-in is pretty interesting, as it'll smoke & smell.