Aprons are one of the top reasons I’m investing in a sand blasting cabinet (I used to take stuff to a local shop, but they went under, so I had to take the plunge.)
You really need to get them down to bare metal and build back up.

dr_nybble has done wonderful work with stenciling, proof it can be done with tools I have in house, and I’m really looking forward to trying my hand at this process.
It’s by far the best method I know of for reproducing the artwork on most aprons - but it’s also labor intensive and extremely fussy. Have to get it right every step or you’re starting over.

Another method that can work acceptably is use of waterslide decals and a clear topcoat. I used them on a Bally Kiss>Geiger Miss World conversion a while back, and it really did work well.
This won’t be as useful on aprons with long “pinstriping” lines, but for self-contained chunks of graphic, this is a decent workaround.
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