dremel with the little polishing disc and the cutting paste didn't help at all. so used some spray paint, just sprayed it into the cap and then use an old cloth to rub it onto the stem. will take a second or third coat but seems to be most effective so far

couple of coats of spray paint were needed. from a meter or so away looks fine, but  up close can still see the branding trying to poke through. not the end of the world, this is intended to be a temporary stem until i find the length i like