Hi mate,
I just basically cleaned up the chequer plate with a scrubber & soapy water. I attempted wire brush on a drill and decided it was taking too long lol
The base coat is 2 coats of industrial grey undercoat (as on tin), this was applied by brush. The top coats x2 was just Halfords Satin Spray which I had left over as I sprayed my other bits of chequer plate with it. I haven't had an issues with the paint coming off, yet!