What sealant should I use between a bronze or stainless skin fitting and a TruDesign ball valve ?
The same options as you would use for sealing any TruDesign composite fitting to a TruDesign composite Ball Valve:
#3M 5200 FT (Fastcure)
# Sikaflex 291i
# Loctite 55 Pipe Sealing Cord
# Standard PTFE thread tape