how do you remove metal bubbling?

[xpress]

i have some bubbling metal that's hard to sand down flat next to the front bumper on the horizontal lip. what's the best way of getting this flat and true for priming and painting?

[Titus A Duxass]

If it's bubbling then it must be rusting, it needs the rust grinding out or cutting out.

[xpress]

it's the bit of metal horizontal to the front bumper, i have sanded and steel wooled down the bare metal so no more rust there but the rust has pushed up on the metal and created small hills and pits into it. i guess it needs more work on the wire brush, it's a hard part to get into to flatten it right down.

[Titus A Duxass]

Okay, now I see.
Try and beat it flat with a hammer and then fill as appropriate.

[xpress]

cheers, that's a good idea. this area seems to be the bane of t25's my mate has quite heavy rusting there as well.

[xpress]

maybe a dremel and a sanding disc could get into it and flatten it out .. :S