1. A transparent yellow ochre: Transparent yellow oxide (Daniel Smith) is my pick.
2. Brushes: The premier watercolor brush is made from the tail hairs of the kolinsky sable, a mink that lives in Siberia. The hairs are naturally tapered at the end and form a beautiful point, but the thicker end of the hair forms a belly to the brush that holds lots of
water. It releases water slowly. They are perfect brushes for watercolor. There are many synthetic and synthetic/sable blends now that work well too.
3. Regarding colors in pans: Some rewet better than others. Winsor Newton sells pans and tubes because they use different formulas for the two. The pan paints have glycerine added to them. Glycerine and
honey are humectants - they absorb moisture in the air. They keep the paints from getting too dry. I just buy Winsor Newton tubes and stir in a few drops of glycerine to make pans. I also add glycerine to other brands for pigments that get too hard to rewet. And yes, that varies by pigment. Some are really difficult.
4. For most paintings, it makes the most sense to work with dry colors and rewet them. If working really big, it's easier to get
enough of each wash mixed if they are wet to start.
5. Getting to know pigments is key - transparent, opaque, staining, granulating. As you are already finding, it depends on what look you want. Artist grade paints have fewer mixes of pigments and more "traditional" pigments with distinct characteristics.
6. Paint brushes come dipped in gum arabic, which is an acacia tree sap. It is also the binder for watercolors, gouache, and soft (chalk) pastels.
7. Gouache is similar to watercolor. It was traditionally used for advertising
art, as its matte finish was easy to photograph. The colors used to have white fillers to make transparent pigments opaque. The pigment particle size is larger in gouache. It keeps the pigment on the surface of the paper. They weren't worried about lightfastness. Winsor newton gouache has stayed more traditional. M graham, and Daniel Smith are two brands made for artists today. They are lightfast and have limited if any white fillers.
8. Paper: The best paper is made from cotton. Cellulose papers work fine too. Paper is soaked in gelatin water (sizing) to add some resistance to water absorption. Some brands also spray the surface with sizing. They all act a little different depending on the treatments. More sizing = less movement. 140 lb is a good weight too work with. Thinner than that, and it's just a wrinkly mess. Thicker = more expensive.
9. Blocks: I buy Strathmore 500 ready cut paper in 8x10 and 11x14 and padding compound adhesive and I clamp and glue edges to make my own blocks. They are cheaper than buying blocks and I get my favorite paper. I have also glued up Arches in this manner. I also make my own sketchbooks using these papers. If working bigger, you need to stretch and tape it.
10. If you hate your hot press paper, use it for colored pencils.
11. Watercolor ground - very useful if you scrub away too much paper and need to fix the surface. Can also be applied to any surface to make it almost like watercolor paper.
12. Watercolor Scrubbers: Jerry's artarama.
12 Mask: Test it out. Some rip some papers. Very handy sometimes. Also painters tape, a clear wax crayon, and scrubbers are useful for getting and keeping highlights.