Getting air in the lines somehow

I am using that same MC from Right Stuff, and I REALLY struggled getting a good seal on the line-in to the second resv. I dont know if this was the best option, I ended up having to use a soft copper crush washer in front before putting the brake line in to really get it to seal down. (I guess also make sure you have your proportioning valve set properly so that you aren't ending up with too much pressure to the remaining drums)