I had tried breeding my best fawn to my tan and found out that that was the way to get a better orange belly on the fawn. silly me! At least it accomplished something useful even if it was backwards. I bet part of it'll be having a^t/a^t; after that I would guess breeding the best tan to the best tan to improve the color. Sometimes these things take finesse, sometimes they take time. I would also guess that not having any C locus dilution would be important. I'd also hazard that some top colors would be easier than others to get the fiery color with. I always wondered if the pink eye dilution made it harder, but then I heard that that actually makes it easier; I'm confused on that. :?:
Maybe the next one in line to answer will have something solid to say on the subject.
PE dilution does not dilute red pigment very much. This is why a red (Ay/*) can be nearly the same shade as fawn (Ay/* p/p). And that's why on a good dove tan (for example), the top color (black) turns grey but the belly color (red) remains the same.
I have a fawn buck, hes of lovely colour but hes not quite show standard, his father was a satin fawn and used in an argente breeding program with his former breeder, only had one litter with me though and litter was 90% satin agouti's.... i was after fawns :roll: always the way!