If you are going to clean it, you are best off blowing out the intercooler with high pressure air. You can also blow down the outside and as Johnny said be carefull not to damage the fins
You can also straighten the fins with a small hacksaw blade if you want to be really sad, by putting it between the fins and moving it up with the blunt side
Make sure that all your connections are tight when you refit the intercooler as you do not want it sucking in dust / dirt