This was discussed not long ago, and a search may help one find the info given.
Here's the B&R jig. It is in my opinion the best one because it swings such that when grinding, it gives the taper on all sides of the pad, and you can adjust the bottom angle on the bottom of the pad with respect to the stock.
If (IF) you have the old pad you can do this without a "jig". First, attach the new pad EXACTLY in the position it will be on the stock an snug it down. Scribe the outline sufficiently enabling you to see it when the new pad is then removed. Grind the sides to include the scribe line and do the same for the heel. Then take the old pad, insert 2 long screw/bolts that fit snug in both pads for alignment and duct tape the pads together wrapping around the center between the screws. At this point you can eyeball the grind to duplicate the angle and the length. It will become obvious to you once yo see them together. Verks, Ollie.
After splattering my garage with sticky black rubber for several years, I finally got smart and sent a couple stocks to Dennis DeVault to have 4 pads fitted. If they look as good as the pads on his other guns then I will be a happy customer!
If you plan to only fit pads to your own guns, the Graco works well and is not very expensive. I have no doubt that the hanging fixtures are easier to use but for occasional use the Graco is fine. Don't overtighten the screws when you attach the pad to the fixture and take your time.
Here is the jig I made. You mount the pad on it with the stock side up so you can view the scribe line. A belt sander works much better than a disc sander because the belt runs cooler due to its length.