I taped some of the episodes of "Beetle Crisis" and in one bit the body shop guy sprayed etch primer onto the bonnet before applying filler, they said this was to help the filler stick to the panel otherwise the filler would slide off the metal like it had been applied to glass.

Tbh this is new to me having always removed all paint down to bare metal first before applying filler and only using thinner based stopper putty on paint as I was told filler never sticks to paint well.

As I have the bug getting shot blasted shortly and the say company will be applying a coat of etch primer to the cleaned shell, I am faced with plenty of filling to get the car paint worthy.

What is the correct way to apply filler then???

cheers

If it's being shot blasted you'll be needing a few 10Kg tubs of filler....
After any stripping of the metal, they'll have to apply something PDQ otherwise you'll have rust everywhere.
Personally, I've used filler keyed to metal (sticks OK when roughed!) and on top of primer/filler and on top of etch primer, with no issues. Celly based stopper just for small pinholes.

Phil.

Ask the company what etch primer they are using, the data sheet for the etch I use states it is unsuitable for use under filler.

Filler will stick like s*** to a blanket on shot blasted metal.

My method is clean bare metal, keyed with 40 grit, filler, flat filler flat.... guide coat, block, if all the guide comes off at a single pass, etch prime and on to finishing.

The company doing your primer should have the spec sheet, if not get the make and google it.

[Edited on 23/9/11 by r1_pete]

I bought some filler t'other day, stated clearly as suitable for use on painted surfaces. Think I prefer bare metal though.
As to stopper, do try the acrylic stopper, it is MUCH better stuff to use than the celly version. Honest.

I always etch-prime bare metal before I do anything else to the panel. After flatting off the filler/high build, I give it another waft of etch to cover any bare metal and then high build for final flatting, normal primer then colour coats (not to be confused with Cullercoats).