Most spray painters would say don't do it because they have access to proper dye based candies, therefore no reason to make their own version with paint and trans base. You can do it with automotive paints if you wanted to, pigment is most probably the same just in a solvent binder. (dont quote me on that)
Paints are pigment based opposed to candies which are dye based although there were pigment based candies ( I still have some old Auto Air pigment based candy however im not sure if there are any brands still available to buy )
Pigment based paints however diluted with trans base can only add colour with the pigment in the paint, which over several layers will become more of a solid colour and possibly stop you seeing what is underneath if you go too heavy, compared to dye based candy which only gets darker in colour but never obscures what is underneath. ( unless you went to the extreme where the candy eventually goes almost black ) but you wouldn't do that.
Yes you can get half decent results from paint in trans base be it opaque or transparent (probably better with transparent paint) or a pigment based candy . I have used pigment based candy myself and it looks ok however, to get a really deep/dark colour you need a lot of coats and it starts to turn more solid. With proper dye based candies you can just keep adding and adding till it gets as dark as you want.
If you are getting the results you want from paint in Trans base then that's fine. There's really no right or wrong if it gives you the effect you want to achieve. it's like using other things with your airbrushing to get the result you want, watercolour pencils, paintbrushes, erasers, scalpels or blades to scratch details. If it works for you then its ok.
Hope that helps
Lee