TUTORIAL easy pictorial for filling bridge, trem or pup cavities.

[nitroburner1000]

Once the dowls are sanded to size glue them and gently tap them in with a hammer until they are seated. Wipe off any excess glue and wait until dry before cutting flush.
You can use whatever saw you like just be careful of scoring the surface of the body. When dry sand flat and fill if need be, then resand until perfectly flush.