I know a lot of guys are dipping frogs, swims, etc. Thought I would post up a little something I came up with to help me.
Worse thing to me was that my plastic got cold real fast. I tried a multitude of things to insulate my cups with little success. Then, as I was discussing mold properties with a buddy, something hit me. (No not my wife...LOL!!) While aluminum sucks the heat away, plaster of paris (pop) insulates or traps the heat.
I decided to make an insulated "cup" for my pyrex cup. Something I could put the cup in and have it hold the heat but also allow me to remove the cup to nuke again when the plastic does cool. Now this still isn't the bet solution but it does help retain the heat in your cup longer.
Basically, I took a 1 gallon milk jug, cut the bottom third off and set my 2 cup pyrex cup inside that piece. Then, I made up a big batch of pop. I poured the pop around my cup slowly until the cup rose up about 2 inches off of the jug bottom. Then I found a few random things to place in the cup to weight it and added the rest of the pop around the sides. Without weight inside the pyrex cup, it would raise up in the pop and be molded.
Let harden and remove your cup. Let stand for pop to dry. This takes days. No need to seal the inside... The result is a mold of your cup. A glove to insulate the cup and a way that you still can just pick up the cup and put it right back into the microwave for further heating.
I will have to re-take pics as it looks like I deleted all of them.
PS If your plastic starts yellowing, add a drop of M-F's iradescent pearl or a 1/2 drop of white (to 8oz plastic or more) and that will help take the yellowing away on the resulting baits.