It doesn’t matter if your medium of choice is watercolor, oil, water miscible oil, acrylic, alkyd, casein, tempera, encaustic, or Genesis paints. You are still painting. You use many of the same skills regardless of the paint. Yes, there are differences but artists employ the same principles of composition, color, value, texture and perspective in all painting. Even sculptors, photographers, cake decorators, garden landscapers, stained glass artists, floral arrangers and architects use those same principles. You can apply what you learn from all the other disciplines to your own work. In fact you should make a point of learning all you can if you wish to grow as an artist.
I find that a familiarity with sculpting lends a greater sense of depth, form and dimension to my painting. My knowledge of color mixing comes in handy when I’m working with polymer clay. An understanding of complementary colors is useful in my work with textiles and jewelry design. I enjoy studying the work of other artists in various fields. I get ideas everywhere and everything I learn enriches every form of art I do.
Of course, as long as you are painting you’ll probably be using a brush (at least part of the time). Certainly many of the brushstrokes we use are applicable to other painting media. Painting is painting after all.
You might also get ideas about new surfaces to use. There are new materials that accept a wide variety of media too. Perhaps you’d like to try handling your acrylics like watercolors and painting on paper instead of canvas. Both acrylics and oils can be used on metal and you can get wonderful effects with that. The possibilities are endless.
Watercolor and oils can both be transparent mediums so some of the techniques work for both. Thin down oils and use them on paper. The oil will bleed but the effects can be interesting. They can be opaque as well. Try painting gouache thickly like oils. Explore making marbled papers. That’s done with oil paints floated on water. Play!
Some media can be mixed. Try using colored pencil and watercolor together. Use acrylics under your oils. Try pastels with watercolor. Experiment. Learn. Create with abandon!