There are basically 2 main types of rifling :
1. Button - a button (small cylindrical tool with grooves in in) is pushed/pulled through the barrel and this "imprints" the rifling into the barrel.
2. Cut - normally a single toothed cutter is again pushed/pulled through the barrel and removes a little metal with each pass. Multiple passes are normally done per rifle groove. A single groove is done at any one time.
Also note that both systems require the tool to be rotated as it moves down the barrel at the required "twist" rate.
Barrels are also normally lapped after they have been rifled.
Bite off more than you can chew and then chew like crazy.