Oh, I forgot:  If you use the method of heating water in the pot, and then
dumping it out -- take some paper towels, bunched up, and as soon as you
dump out the hot water, wipe out the inside of the pot, quickly while it is
still hot.  The paper towel will wipe of almost all of the leftover wax and
propolis.
 
Interesting anecdote:  A few years ago I was rendering some old wax using
big pots like that.  It was mid-late May.  Anyway, I would set the pails of
hot liquid wax (as well as the pots) out on the back porch of my
ground-floor apartment to cool off at night.
 
Well, on my birthday (end of May)(!)  a nice big swarm showed up on a maple
tree right outside my back door, in perfect position to hive!  It was only
a few feet from the porch.  Nice birthday present!
 
I had been storing the gummed up strainer bags, pots, etc. out there, out
of sight, as they start to look and smell pretty bad (from rendering old
brood combs).   The strainers I was using were those strong, mesh laundry
bags as issued in the military.
 
My suspicion is that the swarm noticed all the wax smell, and whatever
pheromones were in the residues drew them to cluster where they did.  It
was right in the middle of an apartment complex, so there were no colonies
right in that central area.  The neighborhood kids got a good show, as I
hived the bees without gearing up, and the swarm was very gentle.
 
If you accumulate clogged or torn strainers or lumps of "slumgum" don't
forget that they are very attractive to bees, especially if the sun can
warm them up.  I have put some lumps of that refuse on the roofs of empty
hives to attract swarms, and apparently it is pretty effective.   FWIW...