Apparently the soapy water thing is a great trick, and also putting a bit of tape along the top of the mask is meant to do the job too
Yeah, the soapy water one is good when you remember the bastard. But you're invariably half way out the M4 doing around 140km/h when you realise you've forgotten to do your visor that morning.
Then you have to resort to the magic breathing technique. And holding your breath. I'd be holding my breath for fucking ages with the vents going waiting for it to clear thinking "I'm sure you get loads of warning before you black out".
The bit of tape one... huh. New to me. Sounds good. Unless you're whipping your mask off when you're back outside I suppose.