https://www.youtube.com/watch?v=EbGUVjOF2uw

He still seems iffy about the value of using WD-40 on crinkle cut finish, primarily because of the smell.

Others use brass bristle brushes for applying the WD-40 instead of nylon brushes.

Hermes Rocket Typewriter Case Cleaning — Crazy Results, Simple Tools

A few hours with some mild soap and water and a toothbrush will clean up most of a plastic typewriter case.

A mild solvent like isopropyl alcohol can generally get the remainder of any tough spots or gummy spills.

DIY Restoring Yellowed Plastic Featuring Royal Mercury Typewriter

Yellowed plastics can be treated with sunshine (or other UV light for several days) and hydrogen peroxide (3%) to repair the yellowing.

WD-40 for Crinkle Finish Typewriters — Does it work??

https://www.youtube.com/watch?v=nz1t6QtARyI

WD-40, which has paraffin wax as an ingredient, can be brushed onto the crinkle finish of a typewriter to clean it up and give it some shine. Use a rag to wipe off excess and take care not to get any in the segment comb. The difference on a generally clean typewriter appears to be negligible and primarily results in a WD-40 smell.

Would something like Armor All work better? Car wax might also work as well. Powder coating polish could work, but it may act as a gentle abrasive as it is also meant to lift stains.

Typewriter Cleaning and Repair Basics #2 Type Bars, Case, and Crinkle Finish

https://www.youtube.com/watch?v=82O_iUAI5og

Segment comb cleaning - isopropyl alcohol (gentler solvent) - odorless mineral spirits - Lacquer thinner (maybe a bit too aggressive) - naphtha (lighter fluid) take care for flammability and ventilation

Work solvent into bearing between type bar and segment comb. To dry things out one can used compressed air when done or just air dry.

If sticking keys not due to being gummed up, bend portions slightly for better alighment.

Do not lubricate the segment comb.

Only lubricate the carriage rails when necessary.

Exterior cleaning

Brass bristle or nylon bristle brushes (toothbrushes) can be used to clean the exterior of the typewriter and/or cases with mild detergents or other solvents. Depending on the finish, try the brush and solvent on a small portion to determine colorfastness and potential scratching first.

Typewriter Cleaning and Repair Basics #1 Assessment and Testing

Recommends against any lubrication on the key mechanism, just keep it clean. Lubrication in some cases may actually gum up the works and cause the keys to return slowly.

He suggests Krud Kutter as a cleaner/degreaser.

How to Clean a Typewriter

Rubbing alcohol or WD-40 for cleaning out light rust, oil, dirt and grime.

Use Rem-Oil for oiling typewriters

Toothpaste and toothbrush is great for cleaning crinkle paint on typewriters.