The wagner is a spit and sputter spray method and for it to work correctly, the paint has to be thinned to its exact requirements. That is always hard to do.
I would experiment with a nice spray rig first. Sometimes I say go and rent one and just try spraying cardboard. This is a good idea, but some rigs at rental places are so shot and have bad heads and all that they do not give you a good try.
Dave, Your a painter and you need to bite the bullet at some time or another and get a rig. Do not get a cheap rig, cheap rigs product cheap results. Get a good rig, spend about $1400. Know your specs and what one does over another. Know your head or spray tip requirements for each job. know your pressure settings for each application.
Once you practice for a while on cardboard or I like just spraying fresh water on an old fence. This allows you to see where you are painting.
Remember, never bend your wrist. You keep the wrist straing and make nice smooth lateral moves. Pull the trigger at the beginning and release it at the end of that run. I work in a small confined area at a time then move to another.
On your laps or your swaths, always over lap the previous lap by one third, some say one half. This gives you a good not too thick coverage.
And one other thing, practice spraying with a gaurd in one hand and the gun in the other. I use my spray shield all the time.
Spraying will increase your productivity immediately. It will also reduce the coverage of a gallon of paint by one half.
Spraying has some dis-advantages, overspray and painting areas that are not to be painted. Wind is a big problem also.
Do your cut ins first and cut in wide. Watch the overspray on the roof shingles right above the roof edging.
Just go and get one. You will say to yourself after this is over, why did I know get one sooner.