If just wanting to manipulate the line between the core and cladding, you can grind the bevels to about 50%, then manipulate. The edge should be about .030-.050" at this point. Depending on the core thickness, the core may not even be showing yet. Once the bevels are basically shaped, use a drawing peen on a blacksmith's hammer to work the edge and cladding with the blade at a full red-orange color. A small forge would be best, but a presto-lite plumbers torch or welding torch would work. I don't think a cheap propane bottle torch for soldering pipes would do the job. You don't have to have a real anvil for this either. A small HF anvil, or even a big block of steel will work. You don't need the whole blade red-orange, but the 1" or so you are working on should be fully hot. Work the blade from ricasso to tip to make it wavy in rolling ridges and valleys. After the manipulation is done, grind it back flat again. Test the look with a dip in FC, and grind some more. As you sneak up on the proper edge thickness, the boundary between the metals should start to show as a wavy line. Again, depending on the core thickness, it may barely show at this point.
Note:
The blade will likely start to curve up as you work the edge. Get the whole blade evenly full red, place on your "anvil", and straighten the spine by gently striking the edge. Straighten any warps and twists after you grind or file down the waves the same way. When the blade is done being ground/filed it should be straight and flat. At tis point it is ready for the rest of the sanding to prepare for HT. The final edge pre-HT for a san-mai blade is about .020".
After HT, start working the bevels down until the blade becomes almost sharp. This should show the wavy san-mai boundary.
