Get a rough drawing, it ain't gotta be perfect. The only thing that has to be perfect is the center line of the guitar to line all the parts up and the scale. I prefer 2 peice body cause the joint becomes your center line.
I use Scotch double sided tape to mount my templates. I use about 5 - 8 peices 2" - 3" long. It never shifts while I'm routing. It's a motherf*cker to get off though, you can't pull the template straight up off the guitar. You gotta twist and pull it at the same time. I also will use 2" coarse sheetrock screws thru all 4 holes in the neck pocket. No holes to fill. Just naptha to clean off the double sided tape.
When making a template, I normally have the guitar that I want to copy on hand. I use a router bit with a bearing mounted on the end. Wrap the guitar up in a couple layers of masking tape so the bearing don't damage the finish. Screw/Tape a 1/2" MDF board to the guitar and go at it. Before I put the MDF on the guitar I trim (jigsaw/bandsaw) it to within a 1/8" or so of the line, so the router won't gag while cutting, just speeds up the process.
I picked up some 1/16" material (brown, looks and feels like tough cardboard). Hadn't used it yet, but you could make a template outta something thin. It's easier to shape & tool. Then use a router w/ a bearing and trace it onto a 1/2" MDF. The 1/2" MDF is what you'll use to cut the body out with. The thinner 1/16" material just helps you make the template, probally could cut it all out with exacto blades and sh*t if you don't have access to alot of tools.
