There are so many variables - soil type, atmospheric humidity, temperature and some others - that it is very hard, probably impossible, to come up with rules for watering. IMHO, 2 gallons or so per week delivered by soaker hose is not likely to be nearly enough unless there has been a great deal of rain. The browning needles are likely an indication of too little water. It isn't tremendously accurate, but reaching down to the root ball with your fingers and testing for dryness is better than relying on some sort of formula. If the root ball feels dry to the touch, water it with a hose. 45 minutes as the tree guy said seems pretty reasonable and I doubt very much if he was talking about 45 minutes worth of soaker hose. Another thing that is very helpful for summer planted trees is to spray them with a fine mist such as that produced by a Fog-It type nozzle. This lowers the temperature, increases humidity and slows transpiration of moisture even if none is directly absorbed. This can be done several times a day. For large trees at this time of year and assuming decent soil drainage, under watering is usually a greater danger than over watering.

Beardeds, right? If you're able to get a root ball they won't know they've been moved (slight exaggeration). If you can't transport rootballs just dig as much root as you can, toss them in a box for transport, and replant as soon as possible. Do not keep them in plastic -- rot danger. Do not expect bloom for a year (or 2, depending upon vigor, climate, soil, ect.) Cut leaves in half if needed to keep them from tipping over, water deeply, and ignore for a month. Then deep irrigation again and ignore.

Ultimately what is the purpose of these plants? Are they to remain potted? If so, how many plants are you able to house and care for? Do you have/are you going to buy 500 pots? If they are to go into the ground, how many do you have room for? It's not as if you can grow on every one of them- don't bite off more than you can chew. You generally just gently break apart the soil and plant each individual in a pre-prepared pot. I handle them by the leaves as they can grow more, but if you crush a stem it's toast. Don't pot great clumps together just to get them dealt with- crowded plants can be stunted and the competition for food and water will be too great. Choose the best of the lot and discard the others. Do this in shade and keep them in shade for a few days after the move until they perk back up. Be sure and have the new pots ready and all your supplies gathered before you expose any roots to air. A spritzer bottle of water can be a good thing to have handy. If you need to walk away during the process for any reason cover the rootball with a wet rag or towel.

Go ahead and move them into a larger pot now before they get rootbound. I sometimes have to repot a couple of times until either the plant is large enough (own roots) or I have the right space.