The best product you will use for interior cleaning is a quality Boar's Hair brush. I use that with a mixture of liquid dishwashing soap + water (10:1 ratio in a spray bottle). This works on leather as well as plastic and the brush does not damage either.
Next: I took a standard 2" paint brush and cut the bristles back to 1". That will give you a fairly stiff brush for areas like the door sills, pedals, switches, etc.
Finally: a compressed air source with a small nozzle is mandatory for blowing the excess solution into a terry towel and drying.
Toto