I've never used gouache, so I purchased a cheap set for use in my Moleskine. It was easier to use in the sketchbook than watercolor. I had a problem with too much water coming from my Niji Waterbrush, but I learned this can happen after pushing on the sides of the barrel to flush the pen. Now I unscrew the nib from the barrel to adjust the pressure. I put the gouache paints into a tiny, toy, metal paint palette, and it and a matching palettte with Yarka watercolor paints fit nicely on the bottom of my pocketbook. It took ages to get the original watercolors out of the toy palettes. Those paints were hard and water-resistant!
Right: Noodler's Ink and Lamy Pen
Noodler's Ink does not like the water-resistant surface of the Moleskine sketchbook pages, so it's not waterproof on the pages, plus it takes a long time to dry. It needs to reach paper to be waterproof. I also showed the Pigma Micron and Staedtler Pigment Liner pens, and they are both waterproof on the pages. Big disappointment because I wanted to use my Lamy pen in the sketchbook. Not to worry. There's more paper around here.