An old toothbrush with some APC will do the trick
It's good practice to go over all the rubbers with a detailing brush and APC before the sno-foam stage if you are doing an intensive wash.
If you are just doing a regular wash try to get into the habit of brushing over all the rubbers, grill, lights, fogs, glass, mirrors, door shuts, petrol cap, etc, etc using the sno-foam.
Just spray on the foam, leave it to dwell for 5mins, and then go round with the detail brush on the parts I listed above.
Then rinse.
These are the type of brushes for the job...
http://www.polishedbliss.co.uk/acatalog/raceglaze-detailing-brush-set-cat25.html
