Wow! Am I glad I asked! THANK YOU, that was a great response, on par with the writings of C.C. Miller or G.M Doolittle. I see that a feeder hose with an excellent anti-drip stop on the spout will be a big help, and a tank that seals in the smell. Also, feed boxes that are wide will help reduce spillage.
I think my routine will change - from one guy opening all the lids while another guy feeds patties, then the first guy feeds liquid, then the second guy closes lids to something more like the following:
Both guys cork all holes, and close all entrances. One guy opens a lid while the other guy covers the hive with a net. After they are all open, both guys start feeding patties, then about two-thirds of the way through, one breaks off and starts feeding syrup. The other guy finishes with the patties, then goes to closing hives under each net, then the syrup guy finishes with the syrup, and goes to removing the nets off the closed hives and both guys open entrances after they are all fed. Corks can stay in for a day or two - make them eat first!
The arrangement you mention is better than the one I was using, forcing a robber bee to go through a one-bee opening and directly through a large, defensive cluster to a feeder on the opposite end of the hive. And, like you say, be obsessive about not letting them get started in the first place. THAT will really help!