Hi....for a lower, tapered incised butt molding, I just pencil in and cut on the line w/ a sharp Xacto knife. Then follow the cut w/ a shallow "V" parting chisel. The line is then straightened w/ a curved "V" needle file. For an upper forestock incised molding, I use the tool pictured below....for a relief carved molding, the incised line is approx. 1/32" deep and the adjacent wood is chiseled off and the remainder of the molding is finished. The 3/8" dia rod rides in the RR groove.
The pictured tool has facility for doing moldings on both sides.......Fred