Hi MiniMe23,
If you care about keeping it in tip top shape, see videos from
Meguiar's UK and/or
Ammo NYC about the two-bucket method, how to wash and wipe the car from top to bottom (particularly in your case with a convertible), as well as third-party products that will really make it shine (claying/compounding/polishing and waxing it once every so often).
But for a normal maintenance wash, a classic jet wash with a two bucket method and a couple micro-fiber towels should be just fine. If you don't even have access to that, there are waterless solutions (which need many more towels though).
Hope this helps!