Paint type advice, cost effective

[funkyFly]

Im just starting the process of painting my bike, once thats done i'll be moving on to a couple of cars.

Issue 1 is : bike is ABS plastic, cars are metal, does certain paint brands use the same hardners and reducers for plastic and metal?

I would seem a waste to by 1 litre of hardner just for 1 bike, and not be able to use it on the cars.

Issue 2 : Again with the waste, is it possible to use the same hardner for primers, base coats and clear?

Also I realise the primers are dirrerent for plastic/metal but what about the base and clears? can i use the clear for plastic on metal?

Is there a paint system that will enable me to do this.?

Thanks