Couple of things about sticking foam, you don't need lots of coats, I found just a single light pass from an aerosol on both bits worked fantastic, and it doesn't come apart at all, have to get it right first time.
Also if a bit of the existing foam is broken or breaking up just cut a square out and stick in a new bit. Just leave a bit for sanding and trimming.
And yes, the fine cheese greater worked perfectly, use it much the same as sanding filler, don't try and get it perfect like filler, it just has to be the rough shape as it supporting the material that's all.
Starting to get shape
I did have a go with an air sander, rips it off at a massive rate, be careful, looks easy on youtube, not so easy in real life.
