what is he doing ?

If you follow this link

http://proto05.x-y.net/pla/2003/gt2/gt2.htm

You will see that the guy that made the porsche sands the paint before he puts on the decals. Why is that ?

It seem to me that he sand down a clearcoat, after you can see the clearcoat polished

you are probably right.

Yep, the sanding was done after the decals were applied and then clearcoated. Done it many times myself when the decals are representing paint, not stickers. - Mark

I've tried to polish a body recently but i really couldn't get an enormous shine.

I used a 2000 grit (automotive) and i wetsanded it. then i tried to polish it with the Tamiya compound (fine).

And i got shine but not more then before sanding it.

What's my mistake ? And yes i've read the FAQ

Sometimes you have to let the paint "re"-cure after sanding.
Try letting it sit for a few days after sanding and polishing, then polish again.
Also, you may want all three Tamiya polishes to remove each subsequent level of polishing scratches... - Mark

Sometimes you have to let the paint "re"-cure after sanding.
Try letting it sit for a few days after sanding and polishing, then polish again.
Also, you may want all three Tamiya polishes to remove each subsequent level of polishing scratches... - Mark
:iagree:
regarding 3 step Tamiya, coarse>fine>finish fantastic to me

also 2000 grit seem really coarse to me for clearcoat: If I have really coarse orange peel I use 4000/8000 grit (wet) or a coarse compound like essebiemme than I work on scratch with 3 step comp.>wax

I can't get the 3 types of compound in Belgium for as far as i know.

Im thinking of trying scratch X

i do it all the time you sand down the base paint before clear it seems to pop more and i think decal stuff sticks better to just base paint.

Yup, sanding back the clearcoat levels out the surface after clearcoating over decals. The way I prefer to do it, a lot of extra work but worth it in the long run. Several clearcoats will be needed, don't try and sand too far at once. Others will disagree with the scale accuracy of this method. Whatever works for you.