How to clean out sills before cavity wax

  1. My model of MX-5 is: mk1 eunos 1990
  2. I’m based near: Harlow
  3. I’m looking for technical help or recommendations on: cleaning cavities before wax

Hi all.

Going to be weatherproofing my 1990 eunos in a couple of weekends time. Looking at using acf50 or dynax s50 in the sills and cavities. They are dry inside but dusty. How best to clean them out before applying the cavity wax etc? I have access to an airline so was wondering I compressed air would work? What have people used?