Or clean the PC when the PC is turned off so the fan motor won't be on ...
Me I just clean them with a toothbrush (you know the one the dentist give you but you rarely use because they are so bad) and/or Q-Tips.
We have a few toothbrushes computer fan cleaners around the office. Even stock the 5 minute hourglass timer (two pictured in box). I recommend the 5 minute hourglass sand timer to aid in applying the proper time, 5 minutes, it takes to properly clean teeth a case fan. I also stock a truckload of hospital quality Q tips. Just the usual case fan checkup and regular cleaning stuff. What is the maximum amount of RAM a 32 bit OS will address? Pull yourself together man.
well first i would suggest you to turn the PC off and then take them out of the case clean the fan area with some clothes,you can use a cleaner too.
then use a tooth brush or a very small cloth (like the size of a screen cleaners) thats what i use lol,
and then for the FAN you could use a cotton bud but be carefull dont press the fan too much while you clean it in case you damage it and then it will be noisy.thats what i use theyre very good