How to Prep Behind the Vents

I've got one of frosts cylinder type blasters... not used it for a while, but I will be using soda, as it dissolves off unlike sand which sits and accumulates moisture!!

 

Putting another water trap just before the gun should help

 

Bicarbonate is the way forward. For your home DIY jobby make a setup much like a air brush, use the air pushing past the pipe into the bicarbonate to suck it up and blast out your homemade nozzle