What might be an idea is to use coloured pencils. One of my old teachers told us to use light blue or cyan for building up the general shapes, and then go over that with regular pencil. But really, any colour would do.
i think revisit the basics, sketch out a simple still life scene in pencil with correct perspective + shadows (the flask for example, the lines hardly show convergance ) if you cannot produce a 'ok' image in pencil, then painting will be even harder.
The only one I know about is grease pencil. There are yt tutes on drawing models with the pencil. But specially that you are interested in hard surface I would use ref images and just standard box modelling. Less snazzy but more controllable.
Day #1 Traveling to China's Culture (Mixed Media) Day #2 Traveling to Greek's Culture (Pencil) Day #3 Untitle (Pencil) Day #4 Visiting China's Culture (Pen) Day #5 Traveling to Norse's Culture (Mixed Media)