48 Ford/Bench bleeding the master

I have a 48 ford coupe and I have rebuilt all 4 wheel cylinder and the master cylinder. I read the proceedure for bench bleeding and I just don't see what it does. I put the master cylinder in and pumped it very fast with out the cap on and the peddel gets hard. I bleed the brakes all the way around. Does anyone know if it is possible to do what I did and not bench bleed the master cylinder or is it possible that I got all the air out. It seems to be holding just fine. Or should I just pull it out and bench bleed. I just think that after you bench bleed and disconect the hoses it is going to leak out anyway. Anyone have any advise. Thanks