I'm someone wasting time sharing my personal experience on how to inject molds with denting problems. The question was asked and I shared what I found to work the best.
(Increase the injection pressure time and the denting is eliminated.)
Coats & Clark upholstery thread 135m 150 yard spools
Hello Hobby upholstery thread
137m 150 yard spools
Breaking strength is high on both threads used and both work well in water.