DFL coating #8 nosecone bearings?
 

I've heard that new nosecone bearings aren't necessarily the best quality. The one from my race motor is slightly out of spec. I'd like to address that, but am not interested in buying a brand new out of spec one. Is there an option to DFL (I wrote DLC inadvertently in the title) coat (or some other coating) a good used one to bring it back within spec?

I did it to reduce friction.. By Industrial Hard Carbon, Denver NC.
The coating is too thin to be much help in taking up some slack but getting it moly coated 2 or 3 times will get you there.

Thanks.

Are there other methods/materials that will give a better result? Or is this not a good idea?

Won’t work. Find a nos one on eBay or somewhere.