I know its on the specialty side of things but I love my UView 550000 Airlift Cooling System Leak Checker and Airlock Purge Tool.
https://www.amazon.com/UView-550000-.../dp/B0002SRH5G
It makes it a breeze to check for leaks and refills the coolant in less than 5 minutes. Don't even need to bleed the system.