Well the last time I used pink bodyfiller, it was a fibreglass-based filler and was waterproof.
The grey is probably primer; in my admittedly limited experience the is no such thing as grey bodyfiller. White and pink, but not grey
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Proud TQE Operator and President of SEFAG - the Society for the Elimination of Ford Automatic Gearboxes

Pacemaker headers + 2.5" exhaust
EF Fairmont interior
MP3 player
Lowered King springs
5 speed manual
EF motor
Newest mod: EF Ghia wiring loom and dash