First I'd say trim most of the excess off the with the table saw you have...
Just kidding. Basically, if you use a rasp, files and sandpaper you have to have a good eye and steady hand to keep the sides of the guitar 90 degrees to the top and back while also keeping the shape you want. If you're planning on rounding the body over a lot than that won't be a big deal. Just a thought.
I always make a template about 3/4" thick first. I make that one as perfect as humanly possible, first by tracing the shape, then cutting out the shape and last I use sand paper and a flat block to get it sweet. I trace the template onto a body blank and cut it out on the band saw. Then I sand it down until it's close to the line the whole way around. Next I mount the template to the body with double stick tape and flush route the body blank to match the template. At this point you can sand it perfect with a flat block and some 150 grit. It takes a lot of time intially to get the template real nice but it's worth it in the long run because you can make guitar bodies the same shape, very consistently.