I dont recall the brand of flush I used, but it was 4x17 oz aerosol can which came with clear tubing and a rubber fitting on the end. I did not make the old txv into a connector, never heard of that. I dismantled the entire system and flushed each component individually.
I probably used at least a can and a half on the evaporator and another can and a half on the condenser, until I finally got clean fluid out. I flushed each component both directions and blew them out with a lot of compressed air.