At our scale thing are not so easy ... :? Behind the guards there is no material, so when you remove them, you find two big holes, and whatever you try to do, the result is very fragile, and sanding smooth some thing that always crack is very frustrating ! :cry:
The way i do need two part molds knowledge, but if i can, then every body can ! :wink:
As you can see from behind, that shoebox bumper had very deep holes behind the guards...

What i do first is to put some modeling clay in the hole, like this :

then i make a resin copy of it...

Now you can sand it smooth, it won't crack !

:wink:












