I like the double cup;neat idea. The plastic should be hard as you can make it on the cups. If you use soft it will just roll over on the edges of the cups.
I like the way you think.
It all depends on what you are pouring and what's in it. Some guys use water but I don't; especially if the bait has salt in it.
I lay my baits out on a stainless steel table that I have. Another material that's good is marble(candy makers use it). I've never used it but I think that porcelin floor tiles might well also.
Did the motor burn out? You have to make sure that the bowl of the grinder does not have any salt left in it after you finish using it or it will rust the shaft of the motor.
I get a year or so out of mine by cleaning the salt out of them after use. The last one I bought was this time last year from Wally World and it's still going.
It doesn't matter how or where you store your salt; it will attract moisture to one degree or another.
I always cook the salt I'm going to use in a pot on my hotplate to completely dry it. The one thing you don't want in your plastic is moisture.
This little 5 minute step will take care of any problems that arise from moisture.
I posted that senario here several years ago. I even included a drawing on how to make it. I don't know if the post still exists(probably not with all the changes over the years).
I called it "the book". When I was painting lures in the early 90"s I used that to speed up production. Once you get into a rythem the clean up of your spray gun takes longer than it takes to paint 100 baits.
No need to buy pricey salt and don't use softner salt because of additives.
You want 100% salt. I find that pickling salt is the best bang for the buck.
Just looked it up. It's a Pico perch 2 1/2". Circa 1971. He got an award from Sports Afield as one of the top 10 lures in the US. Doesn't give a value but my book was printed in 1999. Hang onto them, someday they will have value.
Thanks; but I've been making baits (starting with wire baits to soft and hard) since 1988. You learn a lot by trial and error as well as crusing here on TU.
All you need is a curious mind and ambition.