How to decide when to d-rest

[Evan!]

I've never done a proper d-rest before. My only other lager finished fermenting in 2 days, and was all the way down to 1.010 before I had the chance to mess with it. So right now I have a bock that has been in primary for a week. It started at 1.070, and is down to 1.030. The airlock activity has slowed to a creep, like maybe a bubble every 30 secs. It's hard to really judge the krausen because the near-blowoff left the top dome of the carboy coated in sludge. So when should I take it out for the d-rest? Should I just take another SG reading in a few days and see if it's changed? When is it too late?

 

[Bobby_M]

I don't know what the pros would say, but I do it at about the time the krausen is settled but there is still some visible activity. Another way to say that is do it when the ferment is like 90% done. I have a Pils that went from 1.042 to 1.012 in a week and I slowly brought it up to 68 for the rest at that point. It stayed there for a day and I started cooling it back down. Once I reach 45, I'll rack to secondary and start the lagering at 35.

 

[abt]

I'm with Bobby. I haven't done enough lagering with the same yeast to get to know it well. A d-rest is cheap insurance on a beer you're going to have to sit on for a couple months anyway. Don't quote me on this, but I believe a d-rest can be beneficial even when you're at or close to TG. I generally wait until kräusen has fallen and just stick it at ambient temps for three days. (Usually takes at least a day to warm up.) Then I rack and chill. Others chill and rack, taking care to drop the temp slowly, but I haven't had a problem doing it the "easy" way.
Also, I've heard that d-rests just speed up the lagering process; that two beers, one rested and one not, will taste the same after 5 months lagering or whatever.
There is the diacetyl test, where you put some in the microwave or something like that, to accelerate the nose. Anyone try that?