I cannot believe I never tried this before last night it's so obvious!
Take 1 new specialized 2bliss tyre, which previous experience tells me are pigs to seal the first couple of times.
Put 50-60ml liquid art latex (or chosen posh sealant) in a cylindrical receptacle (jam jar)
Use a paint brush to apply a liberal coating of latex to inside of tyre.
Leave 10-20 minutes for latex to thicken up depending.on room temp.
Fit tyre (with additional sealant based on personal taste).
Inflate with normal track pump.
No need for soap, sidewalls sealed and all done in 5-10minutes plus drying time.
Did I get lucky? Does anyone else do this?