I would have it loose but not all the way off, when you let up on the pedal the fluid will shoot up and can mess up what ever paint it hits.
If you started with a new MC and new lines, bench bleed the MC before installing it then you need to bleed the right rear first, then the left rear, then the right front and the left front being last. You always do the farthest from the MC first or you will suck air into the ones you just bled.
Have someone work the pedal for you and before you have them pump it up loosen the bleeder and have them push the pedal to the floor and hold it till you tighten it, do this three or four times before you have them pump it up, this will move more air out quicker so it will be easier to get a pedal.