I'm making the assets on my own, but there is still stuff to point out:
- Balanced usage of references. It is important to use them, but if you will get tied to them wa-ay too much, it may be limiting
- Preference of speed. I'm not spending an eternity on all assets, instead i try to optimize the development times and use it wisely
- Tools. Each for it's own! I use Blender for geometry and UVs, and i have a custom-made Blender plugin to make it easier to export things for this game. GIMP is used for various kinds of things, starting from icons and ending with seamless photo-textures to use in environments. Quixel Mixer is used to mix up the materials taken from Polyhaven/AmbientCG in order to make them fit better in the world of this game. Substance Painter make it faster, easier and cooler to make textures for props, characters or weapons
Either way, if you have more specific questions, i'd like to answer!