after yesterday's FUBAR I tried some of the advice suggested in oppo.
I did take the opportunity of having 4 centre caps to try different techniques. I attempting spraying the cap red, then putting wax in the recess and spraying white over, fail. I tried spraying white then using frog tape and cutting into the depressions, I couldnt do it without damaging the white paint, fail.
So I thinned the paint and dropped it in, it flowed nicely to the edges. Then after drying I touched up the middle with thicker paint and the result is as above.
In the one below I attempted to drip into the surrounding "ring", epic fail. I think I will be satisfied with just having the H red as above.