I was wondering where common sense would come in and mention cardboard.
On really awkward bits use smaller bits of card and stick them together with parcel tape. It's an excellent method for 3D patterns.
This was for a steel canopy on a slate fireplace.....
Just spent part of the weekend turning & milling a router bit from silver steel. SWMBO wants a Victorian style bead on a cabinet I'm going to make. Very satisfying, very cheap (about 25p) if you neglect the cost of the lathe, mill, rotary table, 4 jaw chuck and milling collet (about £1000..). Why, by the time I get to the 40th router bit, the machine may have paid for itself.
My trade is joinery which I pursue intermittently. I've tried most methods mentioned here and they work. Worked in boatbuilders years ago and the pros actually used strips of thin ply 2" wide latticed around to follow the shape, screw the bits together, put in bits as braces and then lay on sheet as a pattern. Even easier nowadays to stick strips together with a hot glue gun. Scribing techniques still useful for getting individual strips to fit.