Great
Are there any products work to restore compression? Simple answer is no.
How do you remove carbon from the combustion chamber? There are many ways including the water trick you mentioned. Here is an example of it being done.
Many many many people use a product called seafoam. The instructions for use are on the can you just allow the engine to suck it through one of the vacuum lines.
I use a kit from 3M called the fuel system "tune-up" kit...