A few years ago I discovered how to pour a soft plastic lure that didn't require a mold and which I found able to catch almost every species in the waters I fish. It has what has been described as a straight ribbon tail that flutters with the least lure movement. I also started making hybrid lures by using a candle flame to fuse a part of one lure to another and here's where old lure's come in.
Tip 1. if you have finesse worms that are thin in diameter, cut off about 1 3/4 - 2" of the tail end and remove any curl tail. Rig the new lure on a 1/32 or 1/16 oz ball head jig (the jig of choice for any small plastic lures). Cast it out and use and uneven rate of retrieve, twitching the rod tip, pausing the lure and using 1/4 reel handle turns. Every fish species will bite it. In fact, I had a turtle start to swim towards it and would have hooked itself if it had caught up with the lure. (Man those animals can swim fast!!)
Tip 2. take the part of one plastic and fuse it to another with a candle flame making sure not to melt too much of either end. I have craw worms I've never caught fish on, cut off a claw and attached it to a grub or short worm used as the body. It caught fish first time I tried it using the above retrieve. The U-shaped pincer flapped up a down and created a profile no fish has seen before.
I've added tails to grubs after removing grub tails I didn't like to produce a different action as well as increase my confidence in the new design after catching over a dozen fish.
Tip 3. you can shorten a grub or worm by cutting out a section and refusing it with a candle flame. Sometimes one size doesn't fit all and shortening a lure does the trick.
The above is not about totally substituting any of the lures you buy and have confidence in with ones you make, but I find satisfaction in knowing that there are hundreds of lure designs that can catch fish. Just knowing that anyone can discover those designs with a little imagination, opens the door to understanding the effect certain designs have that provoke a fish to attack.