Here's a link to the BEST aluminium to use between you mold halves.
http://shop.hobbylobby.com/products/metal-sheeting-864678/Cut a piece slightly bigger than your mold. Insert it into the mold and press shut. You may need to reopen and cut a small hole at the alignment pins (most of the time you do not). Cut the sprue hole out with a pair of scissors. I then take a razor blade and trim all the sides so it fits exactly..with one exception....The open end of the mold (across from the hinge) I leave about 1" of foil hanging out so I can mark it with the name/size of the bait the plate matches up with.
This will give you a "custom" laminate plate...so to speak. When you inject you will get both halves of the bait in the first color. I typically shoot a bunch in one color....then reload the mold with the 1/2 of color 1 and then shoot color 2.
Works VERY well with stick baits!!!! And fast!!!!!
The aluminum is 36 gauge is thicker than aluminium foil...but thinner than anything you can find at the hardware store. It's thin enough that it does not affect the clamping of the mold but will last darn near forever. This method works well for any bait that does not have a "top" or "bottom" ..otherwise you either have to remelt half the bait...or use on of the laminate plates (which is a better idea than remelting!).
I still like the laminate plates better when available...but this works well.