[sdiy] Old Keyboard keys - repair? & Cleaning old gear

[sleepy_dog at gmx.de]

So as one of the hints in my scrap keyboard thread of weeks ago was:
get (parts of) an old electronic organ.
I did get a manual. But look at 2 keys of it:

https://postimg.org/image/tn0gu4c6b/
https://postimg.org/image/ftc452rar/

(sorry for bad focus, my cam is roughly as top notch as that keyboard there)

Is there a semi-decent way of repairing such a key to make it a) 
playable again without soon cracking again and b) as a bonus, make the 
crack look less obvious? (some sort of paint that won't rub off easily?)


While we're at it - Cleaning old stuff -

While the ebay seller neglected to mention that little issue and it 
wasn't visible on the foto,
he agreed to send replacement keys, but

he actually sent the other manual of the same organ, and its only 
problem is that it is dirty and smells a little :-D
Obviously I now have two manuals, one with need of repair.
Any tips on the cleaning of the crud & ridding it of smell?
Buy compressor + cheap sand blaster? Too bad I can't put the compressor 
anywhere, much less operate without inciting a revolt. Maybe some car 
DIY shop has something like that... *scratches beard*

Nice weekend to all!