I've tried sanding metallics and the results weren't good!Swirls and lines,even with very fine grade wet and dry(used wet).It sounds like your top coat was applied either with the gun(or rattle can?)moving too fast(if you move too slow,you'll get runs and sags,tho!) or possibly too far away or maybe the panel was too warm.
Try flatting it back,with wet and dry(1000 or 1200 grit,used wet with a little soap)then see how it looks.If you can see marks in it,when it is wet,it will look the same if you lacquer it, but you will have a smooth surface for another top coat then with a couple of lacquer coats(rub down between each lacquer coat).
The final clear coat can then be flatted first with 1200 then again with maybe 2000 then t cut or similar then finished with wax.
Before you attack it with wet and dry,though,let the paint harden properly!!.
Just my opinion but as long as the metallic is evenly sprayed with no sags,runs,(flies!really hard to get rid of the legs
) etc it doesn't need to be glass like,just evenly sprayed,and not too much 'orange peel',with no dry spray bits ,like you have now.
Hope that helps a little