My male rottie was definitely male dog aggressive (except little dogs that he allowed to terrorize, chase – I swear you could see him laughing -- and pretended fear of). The best command I ever taught him was "look at me". It enabled me to take him into crowded dog shows and anywhere because the second I gave the command, he locked his eyes on me. I then gave the "leave it" command. Once a dog at obedience (my 8 yr old child did obedience with him for HER practice) a Great Dane puffed up and challenged him. From 20 feet away he obeyed both look at me and leave it. (They removed the Dane from the class permanently.)
Loose leash walking is so simple. You stop, or back up, the second there is ANY pressure on the line. No pop jerk, just back up.
THAT said, if you plan to show, you want a dog working the line to show enthusiasm so don't make the pressure too light, lol. Show dogs don't look good heeling.