Vinylkote sounds like the way to go, but I wouldn't spray either cellulose or acrylic gloss paint directly onto any surface without first using an acid etch primer, which promotes good adhesion to both the surface to be painted, and to the top coat. Two acid etch primers seem to find favour, namely, 'Autotek Pro' and U-Pol 'Acid8'. Of course, the costs soon start to mount up:
https://www.ebay.co.uk/p/1-X-Autotek...d=152435790444
https://www.ebay.co.uk/itm/U-pol-Aci...-/201487926803
No doubt whatever you choose, you'll want to try it on the underside of the SP30 to check if it gives the desired result, remembering - as always - that you can't put lipstick on a pig to make it look pretty.
Good luck with it Michael.