'bollocks it all up' is a perfectly good use of the phrase.
I would guess that the warnings about car 'detailing' products are because they often contain petroleum products, and natural rubber and petroleum do not go well together in the long term, especially it they get to the glue underneath. If I were to turn to any product to refresh the finish (I don't think it can be 'fed' as such) it would be to use a product with glycerine in it, I use a Beeswax based hand lotion.
But if you have any small areas of Vulcanite to repair the best product is called 'Milliput', a two part resin putty that comes in different grades and colours, one being black. Mix some together, spread it into the space and level it down to match the rest of the vulcanite, then use a wet cocktail stick (or whatever tool you invent) to impress a vulcanite pattern into the surface. You get a long time to get it right before it dries, then after a few hours it will have dried just as hard as the surrounding vulcanite. Get it on Ebay or from model shops.
Steve