Morton, no, no spray. Paint of any type most likely won't stick very well to that mat, and if it doesn't it will flake off and make a mess.
You can get a roll of black felt from Bunnings, and apply it to the length of the dewshield that extends over the corrector plate.
Below is a picture of the Corflute dewshield I made from my Mak, showing the black felt. It extends only maybe 20mm or 30mm beyond the rim of the corrector plate rim.
All you then need is a few Velcro tabs down the length of the cut-to-size-and-shape mat to fix the new dewshield in place
You can by black Velcro tabs from Bunnings too, or a $2 shop. The finished dewshield you can just roll up to store.
Alex.