Why would you be using salt for a bug bait? If you use salt, the bait will lay flat on the bottom. If you do not use salt, the bait will stand up tail off the bottom and be seen. Isn't this the objective of a craw imitation? I use these types for flipping and usually use a heavy weight.
I use the the pyrex/microwave method and always wipe the spout with a paper towel after each pour while the plastic is still hot. I find it pours better when the spout is clean of plastic.