SS brake lines... fluid flush inquiry

[Starter986]

I'm going to flush my brake fluid... read/saw the instructions/directions ready to proceed. Waiting on the ordered Motive bleeder.

I'm also going to install SS brake lines. I'll remove the brake fluid cover and remove/install the lines trying to mitigate fluid going all over the place. Waiting on the flare nut wrench set.

My inquiry...

Should first I install the new lines then flushing the fluid with new? Or... flush the fluid with new... install the new lines... then "top off" the fluid?

I appreciate any guidance, tips, and tricks. Thank you.