I got the Harley ones, chrome.
Used duct tape to hold them on a piece of cardboard, then spray painted them twice AKA two coats.
Flat black.
Used the supplied sticky tape that was on the back of the stock.
Applied them when the paint was dried, and 800 miles later still look great and haven't come off.
The underside of them have a ring the sits inside the cam covers perfect, and don't allow them to shift in any direction when applying them. And the tape that came with them was already on the backside, and I think it semi melts when the engine gets hot and spreads more.
They work great, and a can of nice spray paint is cheap.
Oh the flat black I used was a can of high temp type for grills and such.