A few people have asked about filling the bumper area of the GTM, so I have added this page to keep all the info together. The same technique could be applied to any car.

Normal front with bumper in place.

Bumper removed revealing the area that will need filled. This area is then cleaned and give a sand to roughen the area up.

Fill with builders expanding foam. And in a few seconds it will look like this

Leave to harden, following the instructions on the can. Then you can cut down the excess, I used a kitchen knife to saw my way along.

.

Now sand down with a 120 grit sand paper, making sure that the foam is slightly below the finished level, to allow the filler to make up the difference.

Here's how it looks after the sanding, don't worry about the bubbles, this will be filled later and I guess helps the foam/P40 to bond.

.

Now put some P40 filler over the foam to seal it. I'm told the foam doesn't absorb water but better to seal it as quickly as possible.

Now sand down the P40 flat.

grill

Add more P40 and sand again, building up thin layers until you are happy with the shape/profile.

sand again

Now for any slight blemishes use a filler primer like P38 all over the area.

p38

And then sand down to get the contours right. Should look something like this. You are trying to have as thin a layer of P38 as possible.

p38

After a wipe down

p38

Now give the area one final wet sand. 800 then 1200 and it is now ready for the hi-build primer.

primer

After I had coated it with primer, it hi-lighted some small pin holes, so these were filled using knifing putty/stopper, and sanded down again.

stopper

Finished product ready for final prep before spraying.

back in place
back on again
sanded
Body sanded

Masked
Masked up

primed
two coats of primer

sanded
And sanded again

red
Top coats on

assembled
done
And once finished with parts back on car.