I used rubbing alcohol to remove the flux off all my K2's boards. It took a little longer than using the other standard defluxing agents, but its alot less harsh on the components (a fellow ham cracked one of the plastic housing to the power connector using standard defluxing agents). It took me alot longer.. a few hours to deflux the board (and resting for 18-24 hours to properly dry) but it came out beautiful.