I have always been inspired by the sketches and watercolors of explorers, cartographers and scientists who lived before the invention of photography. I have tried bringing watercolors myself, but didn't end up using them, since they ended up buried deep in the pack. I assume that those old-timers must have developed efficient, lightweight methodologies for bringing their art supplies on extended trips where weight, space and ease of access were of major concern and I assume that some of that knowledge is still around. I hope some of you who have a lot of experience creating art in the great outdoors could share what materials to take on the trail, how to carry them so one actually uses that stuff, and techniques for making art when easels and straight table-surfaces are hundreds of miles away.
I've hiked with photographers, painters, sketchers, and writers... two things that will help:
Other than that, just slim down your kit the bare minimum (small tubes of paint rather than big ones, etc.) And if you run out of a color - improvise. Wild art ain't studio art.
On my treks I usually keep a trail journal. I only bring a pencil and some eraser (i.e. super light-weight), and use this to write about the journey, draw small maps/diagrams and sometimes even sketches of what I encounter.
Get a routine
Tip: Do an improvised herbarium