Hi @mat223740 ,
They tools and materials highly depend on what you want to clean and often you need to use these tools. I am pretty sure that you need to have all the essentials which are:
-Isopropyl Alcohol (99% or above)
You can get most cleaning jobs done with these simple and inexpensive tools, from removing flux and thermal paste from the boards.
Canned compressed air is quite expensive for what they are but you can use them as a freeze spray for short detection if you spray them upside down. I use a 9L air compressor to blow off the dust of the boards before any repair job.
If you are a bit more serious about repairing electronics, or you are planning to repair motherboards on a daily basis you can invest in an Ultrasonic Cleaner. There are hundreds of different models available. I highly suggest purchasing one with a big enough tank (3 litre or more) to fit all sorts of motherboards in it. I also recommend getting one with a 'degas' function which gets rid of the air bubbles in the solution before the cleaning process, resulting in a cleaner result.
Stay away from the cheap Chinese jewellery cleaners. When it comes to cleaning solutions, again, huge availability in different products, just make sure you get one which is designed to clean PBCs and not rust remover for mechanical parts.
After ultrasonic cleaning I usually submerge the boards in an alcohol bath to displace water that may be trapped under the chips and then bake them in the oven to dry them out. You can also use the compressed air to dry the alcohol off but sometimes the friction can cause static sparks and could damage some delicate circuits. So be careful.
Hope this helps!