Good add and one more knee-saver on the bike: set your saddle so that with your heel on the pedal at the bottom your knee straightens; then ride on the ball of your foot so you keep a slight bend and take pressure off the front of the knee. If you like numbers, keep that 20-minute block at talk pace or roughly 60–70% max heart rate, and bump total weekly time by about 5 minutes every other week. On non-bike days, a quick set of glute bridges and chair squats in a pain-free range builds the support your knees need.
Co-signing the warm/cool primary idea - if you want an easy start the Daniel Smith Essentials 6-tube set or the Van Gogh 12-pan pocket box hit that palette and are easy to find on Amazon. Skip the bundled kits and grab one decent synthetic round brush (size 6–8) instead; it’ll do 90% of what you need. Also, paper matters more than people think: even a budget watercolor pad like Canson XL will give you the flow and lifting you saw in tutorials, unlike notebook paper.
