Custom Fiberglass system

Hey guys. I was wondering if anyone know the best way to get a correct fit for a system. I know who to fiberglass thats the easy part. The hard part for me is to figure out how to get an exact fit. I dont want any play. I ask only because i want my subs in my trunk but along the sides. And i also want my amps to face the back. Any help would be appreciated. If i confused you let me know. :1zhelp:

cover the area in aluminum tape, then in masking tape. Then resin an area, lay fiber glass, resin an area, lay fiberglass. Keep repeating that. there's a link floating around somewhere for DIY'ers.