The way I do a Diacetyl rest is to warm the beer before the end of active fermentation (one or two degrees Plato to go, or 4 to 8 gravity points). The residual diacetyl will form at higher temps, and the active yeast will re absorb it fairly quickly.
If you are an AHA member you can look up the seminar by Kara Taylor at this years NHC, lots of good information there.