Detailed coolant fill process?

[Junkley]

My 2001 Boxster S suffered a busted oil cooler. I replaced with new seals. I got oil in coolant and now I’m flushing system over and over and I’m sure I’m not doing it correctly. I do not have access to air. I’m having to do this on the side of the road. Pouring from drain pan into buckets.

I’ve flushed with Shout once, and now in second go with Blue Devil degreaser.

Can someone please tell me the exact, detailed steps to fill coolant quickly and correctly.

Thanks,
2001 BOXSTER S