Regarding rendering the old combs in a solar wax melter.  I had the exact
problem.  The root of the problem are the old cast of coccoons or larval
skins that line each and every cell in the old brood combs.  They act like a
sponge to keep the wax from draining down into the drip pan below.  And I
found that leaving them for days or weeks didn't improve the process.  In the
old days, I simply threw old combs away because I knew that I couldn't get
any wax out of them.  Later on, I found that I could get a fair amount of wax
out of them by boiling them in a hot water wax press.  I got an very old
discarded aluminum cooking pot.  I wrapped the old comb in burlap or
cheesecloth covered with water and boiled it outside over a propane burner.
When it starts to boil, it has a vice screw that pushes the melted combs down
to the bottom of the pot and allows the wax to gather at the top.  After 60
minutes I turn off the burner and let it all harden.  When done I have hard
wax on the top and the "slumgum" at the bottom of the pot.

Hope that helps.

Randy Lynn
Greensboro, NC , USA