For black plastic, had good success with a Mother's product called "Back to Black" available at most retailers here in N.America. I just used some on an old parched plastic wheel arch and now its looking like new. If it just needs a little spruce up form dirt and dullness, try ArmourAll plastic/vinyl treatment. I prefer the low gloss type on most car interior surfaces.
ACF-50, as mentioned earlier, is really a good anti-corrosion treatment meant for metal work. I'm sure it will give a shine to old plactics, but it is an oil and not really a wax or plastic treatment. I'd thinkj WD40 will achieve the same results as ACF50 will on plastic...but likely not last long as proper plastic treatments and both will leave residue for future fingers to pick up.
Edited by Tornado99, 07 August 2020 - 05:19 PM.