Definitely wash, and there are some mold lines in tight spaces/on tight curves and found that having both a straight X-acto and a curved blade (like this) really sped up the process.

And also the plastic they use is weird and when basing them definitely use a superglue (not a plastic glue) like Gorilla superglue or Zap-A-Gap superglue. For the arms and headsthe Citadel plastic glue has worked fine for me so far.