I use this:
Makita 18V LXT Lithium-Ion Cordless Blower, leaf blower, car dryer, rechargeable blower
I already had an 18V Makita drill and driver set with extra batteries and a charger.
Found it on sale once at the Rainforest web site for $59.
Actually bought it to blow dust out of people's computers. With the 3AH battery pack, it lasts about 12 minutes on high, which is just barely enough to dry a car if you work quickly (no wasted hot air:xyxthumbs

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I had tried all of the Metrovac computer line, and even the big one wasn't really strong enough to get the dust out of fans, heatsinks, etc. This thing does great on that stuff.
I'd say the components are too expensive, unless you already have cordless Makita tools. Then, it's an alternative.
Jim