HI, I have tried this.
First up... make sure your mould or press mold is quite firm when made. use alot of blue and little yellow compound.
or
as i did use a FIMO, DUKIT or polymer clay... press it with some cling film on one half or a covering of vasaline or cooking oil.
Then bake it in the oven as normal but either remove the cling film or let the oils run off or burn off... may need some ventilation and to turn off the smoke alarms for this.
Ten when you have two parts to press mold try and press it on the wire and use a very tough or stiff putty to cast with. I use Milliput as itg can be ground or filed into shape better than GS can.
Somewhere I think I saw someone write about mixing putties together too.. GS and milliput and aother types.. which gave a harder more resilient copy.
Hope that helps... but it is real hard to do.
I made new bows on some models that had broken bows using Milliput.. look
http://lighteffect.net/blogs/?p=1051