One thing to take particular note also when removing the boards to clean. Thoes ribbon cables that connect the sandwiched boards together - they get REAL fragile over time and can crack very easily, rendering the cables useless.
I've read somewhere that SCSI cables with a certain type of connector on either end is an excellent substitute, but haven't tried it myself.
Also, Bob Roberts sells these SCSI cable and ribbon kits on his site.
Lastly, and "No" this isn't BS - I've heard the BEST way to clean PCB boards is in a dishwasher. Yes, I'm not kidding.
In a nutshell (And this is just from what I remember and NOT to be used as actual instructions (There, I've said my disclaimer
Remove all socketed chips and set them (making sure you have some way of
knowing how to add the chips back in proper order)
Place the PCBs in the dishwasher
DO NOT add detergent
DO NOT set to heat dry
Run the washer
Once completed, pull the boards and lay somewhere where they can air dry
as quickly as possible
I've never done this before to my boards, but many people swear by this. I've
even read one collector who has a dishwasher in his garage hooked to a distilled
water tank JUST for the purpose of cleaning boards.
I wouldn't recommend this proceedure however, until you speak to a person who
has actually done this and might know of some steps I might have missed above.