I saw someone else do this n went why not
More detailed notes:
Corner is bad:
Never go up to that top corner, unless you're looking to burn some eyes. It's too saturated, choose more inwards.
Shade with colour:
Unless you're shading black and white objects/characters, always use different colours to shade. you can use a darker or lighter variation of the colour your shading over, or you can use oranges/browns for warmer tones and blues for cooler.
If you need to experiment, clip a new layer to the colour layer and turn on "sample all layers". This will ensure watercolour won't do that weird white effect, and that you can delete the shading if needed.
Experiment:
There are a lot of different brush types you can use. find one you like.
Pick colours that match:
Bad colour combos can ruin a character. Make sure they match. If you can't find shades that work, try looking up a pallet, for example "yellow and blue pallet". You can use https://html-color-codes.info/colors-from-image/# to pick hex codes, and click on the solid colour box in the colour section on oekaki to put in a hex code.
Erase for detail:
Erasing the edges of your lines can give it a really nice look. It will take longer, but its worth the effort if you do it right.
I hope this helped someone in some way!