Well, many of the buffs I see are not nearly as dark/bright a golden buff as the standard calls for. They should be the colouring of a gold coin ("guinea gold," with a guinea being a very old-fashioned name for one pound sterling coin minted in gold rather than silver. (I don't know how to make the pound symbol, or I would use it). So darkening the skin in a buff will help with the shade of the plumage, but to the possible detriment of the undercolour. Buff is a VERY complicated colour, and there are a lot of genetic ways to achieve it.
If I had breeding experimentation space, I would try to breed E^Wh/e^b buffs on the theory that it might mesh the best of both: darker gold feathers and darker skin with less smutt in the undercolour. But buffs are not my current focus, and I already have too many projects without enough time to add another. So, your best breeding bet is to find birds as correctly coloured in all areas as possible and work with them.
As for barring/cuckoo, the gene does so much dilution to the skin that you need to make sure that as many melanizers as possible are bred in if you are ever to achieve skin that is even close to the standard. IMO, the boys should not be bred to be homozygous; that lightens the skin and comb even more.