If it plugs into the cigarette lighter, it will be quite slow. A good bicycle tire pump may well be faster but more effort and still rather on the slow side.
If you have a generator, I would suggest getting a small AC powered compressor. I have and am very satisfied with a Fini AirBoss compressor, which is quite compact, and shaped something like a suitcase. Sears also sells the same unit rebranded. It came with a proper air hose with quick-connect couplers that's long enough to reach any tire on my class C when it's plugged into the outside outlet. (It also has a separate little tire inflation hose built in that I have never used.)