TECH GURU's out there, how to clean Circuit Board?

There are several products made to clean circuits. If it weren't pouring down raining outside I'd go out to my car and get one so I could read the label to you. Find a product made for contact cleaning, get a small stiff brush, and go at it gently. I like to use acid brushes (that's what I call them). They are about six inches long with fairly soft bristles. I cut the bristles to about half their length for firmer brush.
I do this all the time. If the board is removable, take it out and saturate the offensive area and brush if needed.
This is not a problem if the proper product is used. Be careful because as one of the previous posters pointed out, some can harm plastics. Good luck and let us know the results.

Eldartford, I used the name contact cleaner as a generic name, my mistake. I brought the can in and here is the info. The brand is Chemsearch, the can says Lexite PS, Electrical Cleaner Dergreaser, the label states "safe on plastic, rubber and plastic - no residue - no disassembly required." I have used this on circuit boards repeatedly to remove residue from spills, leaky caps and rodent urine and fecal matter (disgusting). This stuff works pretty well without harming boards. Given time it may cause some deterioration but I haven't noticed it. The residue is probably more harmful than the chemical.
Now I recommend first cleaning the affected area with denatured alcohol and a brush and then spraying the cleaner. That's how I do it. Good luck.

Looks good as new in pics. Kudos on a job well done!