Stereo equipment isn't the same as a synthesizer - but it's close enough I would think. The cleaning tips go one step further than the recommendations in MODX's manuals. See the part about cleaning oil off of remote controls.

https://hub.yamaha.com/audio/a-how-to/spring-cleaning-special-how-to-dust-and-clean-your-audio-gear/

Myself, I just leave the oil and grime and what have you on the keyboard.

Search the net enough and you'll find keyboard owners who report trying this or that and what's been working for them. There's a company that sells stuff you spritz out into a cloth and they're happy to sell you something. Maybe someone with a MODX that has cleaned their own smudges will give a better endorsement of a particular approach that can work for you.

Funny, and nasty all at once...I kid, kinda ,thank you for the reply. I m thinking about trying a little Murphy's auto vinyl cleaner/conditioner. On the back first 🙂

Page 4, MODX Owner’s Manual:

“When cleaning the instrument, use a soft and dry/slightly damp cloth. Do not use paint thinners, solvents, alcohol, cleaning fluids, or chemical-impregnated wiping cloths.”

Get a quality micro-fiber cloth.
(The MODX is not an automobile!)

I will do it first, thank you

And for dust I use a soft paintbrush. It gets in between all the knobs and sliders.

If you're cleaning a surface that isn't sealed - say like sliders - then using a paintbrush will move around the dust and maybe allow you to pull it out from under hard-to-reach places but also pushes it into the slider tracks. What I see from pro restoration videos for dust is use of a vacuum cleaner to suck the dust out rather than possibly pushing it in using a brush.

Reference the CS80 restoration video from Syntaur as one example.

I just get my vacuum cleaner with a soft bristle brush attachment and gently go up and down.
When Bad Mr keyboard gets dirty he just opens up a new one 😀