I use lint free cloths which I buy at staples, and 97% alcohol, or denatured, which is better, evaporates instantly, but 97% alcohol works, just dont drown the chip in it and yeah scrap with finger nail works too!!!
If the paste is really dry and hard to take off, soak a cloth or paper towel with rubbing alcohol and rub off the paste. Otherwise, use alcohol soaked qtips to remove the paste.
Personally, I dab the old fashioned rubbing alcohol onto a Q-tip and smear the surface with it. Then, I use a toothpick to comb over any potential missed spots. It's cheap and effective.