Hello, frank & welcome to the fold ! I always use superglue. It dries fast, won't shrink like putties, and can be buffed to match the plastic. The answer to your question, though, is what works best for you. Have you checked out the techniques section ? You can, no doubt, find more information there of the pros and cons of different fillers. All of them work, its only a matter of finding the one that best suits your needs. Good luck, and welcome again !