Plumber's Tape. That would have been my suggestion…. once.
A boiler-testing seminar I attended in Taunton last year (? 2017?) said NO to PTFE tape, admittedly for boiler mountings and test-plugs, because small shreds can escape and cause trouble by blocking small steam and water ways. Where the fitting is up to a shoulder, as it usually is, use a thin fibre washer. I'd add, or where the design allows, an O-ring in a correctly-sized groove in the joint face.
I've certainly noticed a lot of people use umpteen turns of PTFE tape on a finely-threaded fitting as if more means better, but it never looks quite right. It does force surplus tape out of the joint.
Wondering the professional Plumber's view, I asked a friend who is a central-heating installer and accredited gas fitter. He says he uses pipe sealant, but very rarely uses PTFE tape, less than one small reel a year.
I have heard it's really a thread lubricant rather than sealant, but this probably in pipe connections that rely on BSP Taper threads, so tightly metal-to-metal. That is all right for heavy steel pipe but not robust enough for the much more delicate fittings on our miniatures.