Never mix fluids if you do not understand its chemistry! People have died and worse from e.g. toxic fumes and spontaneous ignition!

Get a can of liquid air to blow away dust, fluids or other stuff (pro tip: get a compressor)
Get isopropyl alcohol for cleaning PCBs. You might also like fixing joysticks, analog sticks, encoders with isopropanol and air.
Get brake cleaner to remove any grease (can also be used to clean PCBs).
Both isopropyl and brake cleaner work good on removing sweating of plastics.

Get chain-cleaner for your bike, which is basically a solvent and some oil (still needs greasing afterwards!).

Only use contact-spray if needed, better try isopropyl first!

Use vinegar or citric acid as a descaler to dissolve limescale - NO scrubbing!

Citric acid is used in so called “bath bombs”, reacting with baking soda.