Derek,
Good advice from Pete & Mo.
Worth checking Carol Hall's site as the drawing of the bird was straight on wood as far as I recall. In the 2019 handout, Carol says:
" Inktense pencils are water soluble ink pencils. Once wet and dried, each layer is sealed and will not move. Multiple layers can be appplied over the top of each other. Because of this, I only use Inktense pencils".
She also mentions elsewhere the use of fixative- Aquanet hairspray (don't we all use this??) is the same as Artist Fixative.
There's also a mention of ChromaCraft Clear Sealer so check her website to make sure you get the right info.
Or just call Derwent?