"THERE IS MORE THAN ONE WAY TO SKIN A CAT"
Buckeye has developed his method and it obviously works well for him. Nice looking pipes, I congratulate him.
As to how other makers do it. I'll share some info with you. If you look at my avatar you'll see a Castello artisan applying the rusticated finish to a "Searock" pipe. This meathod is used by not only Castello but some other Italian high end makers and some American makers, including myself... back when I made pipes.
First you don't need a Dremel tool to use this method but you do have to make your own tool or tools... Home Depot doesn't sell them. What it is is a "gouge". Mine, and I have 3 different ones, consist of a piece of 3/4" to 1" wood dowel about 3" long. At one end I drilled several holes the size of the nails I'm going to use. The I cut the heads off some nails and stick them down it the holes with the points facing up and protruding about a quarter inch above the dowel. Secure with glue. Then I would finish it off by putting a collar around the dowel where the nails came out for strength and make a "T" handle for the other end. The nails don't have to be perfectly aligned or straight... this is not a precision instrument! The bigger the nails you use the larger the pattern you get on the pipe and, or course, the smaller the nails the finer the pattern. You can even drill one large hole in the dowel and pack all the nails together if you wish.
Now that you have the tool here's how you use it. You need something to hold the pipe. Most makers use a block of wood with a tapered post sticking out of it and they shove the pipe bowl down on it till it's secured by friction. They then lock the block in the work bench vise in a position so they can work on the pipe... moving it occasionally as needed.
To "texture" the pipe you take the tool and putting the nails on the pipe you PRESS AND TWIST. This will start to first make deep scratches and then gouge away the wood. You keep going, covering all areas you wish textured until you have the desired effect. The beauty of this method is the randomness of the effect. After you're where you want to be you can buff the pipe with a wire brish to take off any sharp or loose pieces and apply the final finish. To get into tight spots, like the inside of a bent pipes shank a smaller diameter tool with a long handle works well.
That's it. Now you all know the "secret".