I doubt you can produce Coolants on 5 plantets in the same system. But if you like jumping around…
I produce Coolants and much more in a wormole, it’s easy money, because taxes are lower, but also it’s more dangerous and you need a Cita to live in.
I recommend Command Center Upgrades and Interplanetary Consolidation to be skilled up to V to enjoy PI. Highsec is not known to be very lucrative, but for a try it’s cool.
Dont forget to skill the Epithal 