For a car, though, the body will probably look bad if you brush-paint it. Like I said, an aerosol can of car paint will work fine, and if you use it in the garage, shed or garden (being careful of which direction you spray in!), there probably shouldn't be any complaints about the smell

Both. Different types of glue will have different properties, and that leads to everyone having their own preferences for which to use. I rarely use tube cement, except when I need to join very large pieces and need time to get them into position. Liquid cement is generally easier to apply, IMHO, and more accurately, because you put it where you need it with a brush and it will run along/into the join.

But even here applies that not all cements are created equally. Tamiya Extra Thin, for example, is called that because it's thinner than Tamiya's regular cement, and those by other manufacturers may be thicker or thinner still. My advice would be to buy a bottle of liquid cement, of whichever manufacturer you like, and try it out.

(FWIW, I don't even use a "real" liquid cement at all, but a solvent mixture sold as a degreaser/contact cement thinner in hardware stores here in the Netherlands, but which also dissolves polystyrene so it works very well to glue model kit parts. However, this stuff is so thin that I use Tamiya Extra Thin only when I need cement that evaporates more slowly than what I otherwise use — for most people, it's the other way around  )