There was a long thread here on diluting the color developer 1+9, developing for (IIRC) 9 minutes (instead of 3:15), and one-shot, naturally. Now I can't seem to find it, or the user who started it.
An alternative I'd suggest is, instead of going one-shot, consider chemicals that last almost forever. I've used the Dignan 2-bath C-41 color developer (which you have to mix from raw chemicals, but none are hard to find or particularly hazardous). The first bath contains the developing agent (CD-4), preservative (sodium sulfite), a buffer (sodium bisulfite, to prevent an alkaline pH), and water. The second bath is just sodium carbonate and a little potassium iodide.
The first bath last almost indefinitely (you lose volume by carry-over into the second bath -- this is the actual developer that's doing the work -- but the stuff never seems to get weak), and the second bath is almost free; use it once, and down the drain. You'd then use a standard C-41 or ECN-2 bleach (which you can mix yourself from potassium ferricyanide and potassium bromide -- and this, too, lasts a LONG time, and likes air), and any neutral or alkaline rapid fixer. The only commercial chemical you'd need to buy is the C-41 Final Rinse, which has some ingredients that aren't in PhotoFlo or other B&W wetting agents, and isn't practical to mix for yourself (AFAIK).
As a bonus, the Dignan two-bath doesn't require 100F +- 1F (or 102F for some kits, which assume your tank will lose some heat during development); it works fine at 80-90F and doesn't care where in the range (I've used it at 75F, but the results weren't stellar that cool). In my old, uncooled darkroom I usually didn't have to do anything about temperature with this, at least in summer; in my new, over-chilled one, I'll still need my
sous vide and a water bath -- which I need for Df96 anyway.
You have to buy about a ten year supply of CD-4 to mix this, and a few other chemicals that don't cost a mint -- but once it's mixed, it costs less to process your C-41 than to use D-76 for B&W.
