John, check on back in the north country. Not too bad up here, full on spring. Snow was thankfully long gone by the time we arrived.
I am using good old 63/37 rosin core solder, which has always worked very well for me. Not sure what would be any better? And I have only been soldering stuff for close on to 60 years or so.
Maybe a quick dab with TixFlux just before soldering might help, I may give that a try.