What is the ideal environment for prepping larva?

[David LaFerney]

When using one of the methods where you turn frames of regular cells pointing down to simulate queen cells what is the ideal environment for doing the manipulation - killing extraneous larva or whatever - and how much time do you have to get them into the cell builder hive?

I think that my best chance of doing this successfully would be if I can use a lighted desk magnifier on my work bench in my non climate controlled garage - my wife probably wouldn't go for it on the kitchen table.  It gets pretty warm in there on any sunny day which I am thinking is good.  I've never seen it mentioned other than to do it in the shade and keep them covered with a cloth.