I've been using this for all my cars and it's pretty awesome. https://www.ecstuning.com/b-schwaben-parts/coolant-refill-air-purge-tool/003466sch01/ Basically, you bleed the system and it'll hold a negative pressure. Then using that negative pressure to remove all the air and fill it up with the proper coolant. Genius design. Here's the manual for it, Coolant Refill / Air Purge tool.