) is to assign a number to each panel and then indicate that it is part of a larger work i.e. 2/3 meaning second panel of three in total) in the same way people do when creating a run of prints Signing a pastel drawing - where you've not covered all the paper is easy enough - however it's not easy to sign a pastel painting where the whole of the support is covered.
In addition some surfaces work better than others if you want to include your signature as opposed to a monogram.
You can also try leaving a question - see comments - and I'll try to point you to where you can find the answer If you only sign one panel of a diptych or triptych what happens if the painting gets split up either accidentally or on purpose. The safest thing to do if creating your own diptych or triptych is to make sure every single panel is marked with your name even if you only sign one on the surface of the painting.
You could choose to only sign one panel on the front of the painting with your signature - to indicate this piece of art is one piece as opposed to two or three.
Nothing worse than an orphan tych of a diptych or a triptych that wanders the world unknown.
I correct the Y's, Z's and any tails on the bottom free-hand and I am done . I can do many paintings at a time with this method . Furniture makers sign their work , glass blowers, pottery makers and take great pride in their sign. My instructor has an MFA and is a working artist and known in the Bay Area.When you paint over it, the paint will settle into the area and your signature will appear on the paper, somewhat darker than the surrounding area.You can also do the same thing by painting the area first, waiting until the paint has a sheen on it, and then signing your name with the stylus or empty pen.There is a comprehensive resource available online for all those who are trying to identify the signature of an artist - and who are willing to pay for the service.John Castagno has been researching Artist's Signatures for years and in the process has indexed and creates a comprehensive database of signatures by time period and continent across very many countries It represents an amazing resource that helps to identify the signatures, monograms and initials of thousands of artists His research is made available in two different ways - via: Another three volume series - this time about the Signatures and Monograms of American Artists.