While the plastic dip might do the job, I don't think it is a good idea.
Snakes are going to struggle when restrained. Even gentle grasping with a pair of specially designed snake tongs can break ribs and cause internal injuries (remember - a big snake's ribs aren't much thicker than a pencil lead!). Using a pair of "grabbers" that weren't designed for this task is even more likely to cause harm.
One of the beauties of the better tongs that are on the market is that, in fact, they allow the snake to slide somewhat within the tongs. If you plastic coated them, the snakes wouldn't be able to slip through and would struggle more violently, increasing the chance of breaking bones, damaging internal organs, and tearing the skin.
If you are really interested in saving these snakes (which I applaud wholeheartedly), you should get/make yourself a snake hook and learn to hook the snakes into a 5 gallon bucket with a lid or some sort of similar container. Then they can be safely moved to a new location.
You should also be aware, however, of recent studies with radiotagged rattlesnakes. It has been shown that snakes that are relocated never settle down and wander around trying to reorient (?) themselves. They apparently do not eat and have a greatly increased probability of being killed by cars, predators, other less benevolent humans, etc.
Therefore, when you "relocate" a snake, you should do it as close to the area it was found as possible to give it the maximum chance of survival. I like to try to release snake within 1/4 mile or less of their capture spot if they must be relocated. I don't know if that is really close enough to prevent their untimely deaths, but at least I tried to do the right thing!
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Chris Harrison