Coming in a little late...but here's my 0.02 $currency_unit..
I use those alcohol-based multi-cleaner (the ones for car-use; mine is
from Johnson), a toothbrush, and a wet-vacuum cleaner..
1. Spray multi-cleaner liberally on MB.
2. Brush vigorously with toothbrush, taking care of fragile components.
3. Use vacuum cleaner to suck up the residue grime/dust/dirt soup.
I find it very effective and it leaves a very nice clean lemony (depends
on the cleaner of course) smell on the MB/PCBs.. :-)
/wai-sun