The best material is aluminum.
As for the pop detail getting washed out when you seal it; I use several coats of thinned epoxy. Make sure the epoxy is thinned down quite a bit and you won't loose that much detail. It may take 3 or 4 coats to get the shine you need.
Push the baits down in so that just a little is showing. After the mold is set, remove the baits and with a large,straight knife, level the top of the mold by scraping the pop. This will make all the openings the same size and a little cleaner. Trim up the rough edges and seal it.
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