There are several ways you can manufacture burn marks or accent your pens and other work ...
Take a piece of really sap-full wood that contrasts in color (darker) and hold it against your nearly finished piece for a few seconds at high speed to burn the resin color into the workpiece... (very similar to what you did, but it adds additional color to the piece ... cedar, cherry, or mahogany for red ... ebony or blackwood for black ...)
Hold some steel piano wire (use holders on the ends, the wire will get VERY hot) to cut/burn a mark into the workpiece as it spins at high speed ... (leaves a burn line around the pen - several in a row can function as a grip)
Cut small lines around your workpiece and glue some copper, brass, or aluminum wire into the line so that it just barely stands proud of the wood (use CA glue) and sand it back to match the surface of the workpiece ... (Gives a metal inlay of the desired metal)
Cut wider and deeper lines around your workpiece and glue some crushed (think rice grain or smaller) stone into the line. Use a semi-precious and fairly soft stone, like (blue/green) turquoise, (deep green) malachite, (red) jasper, (yellow) serpentine, (deep blue/purple) sodalite, ect ... Use CA to glue it in place, and leave it just a little proud of the pen's surface. Sand it back to match the pen contours. If there are any voids where a piece of stone can go, stop and glue some more stone in, and repeat till you have a beautiful unbroken surface. (Gives a crushed stone inlay of the desired color genuine stone)
There are many other ways to accent your pens as you make them, none of them are wrong, because they're all beautiful to someone!