I had an Encore azalea for 2 years, then it became a victim of being shoved behind a bigger tree and dried out too much between watering.
I can see why Stan would consider Encore as undesirable compared to Satsuki azalea. His observation are more or less correct when comparing Encore with Satsuki or Kurume azalea.
However, of the list of trees "totally unsuitable" for bonsai, which includes Catalpa, Walnut, southern Magnolia and a host of other things, in general all azaleas have good potential when compared to that list. As Gig showed with his photo, they can make an acceptable for home or hobby level bonsai.
You can make decent bonsai from an Encore azalea. For the same time and effort, it won't be as refined as a Satsuki, but it can be quite nice. Problem is it will always be judged by Satsuki standards, so if awards are your thing, it won't do. Embrace that an Encore azalea is not a Satsuki and it won't cooperate the same way a Satsuki would. You can certainly make a decent bonsai from an Encore azalea.
Because Encore will flower off and on throughout the year, the presence or absence of flower buds is not a good guide for when to perform techniques, You will have to learn to read the health of the tree in front of you to decide what to do and when. what the bulk of the vegetation is doing will be your indicator. Repotting, especially if you are going to do major root work, which includes cleaning out nursery soil and replacing it with a more suitable bonsai substrate, this should be done in very late winter or early spring, as you see signs of the tree waking up from dormancy. In my climate (relatively mild summers, very cold winters), I have had good success with repotting middle or late summer, for me August 15 through Sept 1. This is early enough new roots develop and harden off before winter, late enough that foliage is hardened off and leaves are in the positive for producing energy. (as Ryan Neil would say, state of positive energy production). Usually for late summer repot I don't do drastic radical root work.
For drastic root work I think the late winter, early spring, as buds begin to show signs of life, but before new leaves have unfurled is best. I would not ''slip pot'' now, just limp it along another month or two as is and repot in spring. Then do the serious transition from nursery pot to bonsai training pot with all the necessary root work. In Virginia, spring is not that far away anymore.
Anytime you repot, do not allow the azalea to bloom out every flower bud it produces. Three months before repotting, cut off most of the flower buds. I always leave one or two, otherwise, what is the point of working with azalea. If I didn't want at least some flowers I would have bought a boxwood. I hate boxwood, it is a boring species. Do not allow more than one or two flower buds develop for at least 6 months after repotting. This will allow the energy to go to the production of new roots. When an azalea does a mass blooming this is a major energy drain. Don't do radical root work or pruning work just before a massive blooming or for several months after, or you run the risk of weakening the tree. An azalea can thrive being allowed to bloom out completely , if you don't throw major stressors at it just before and for several months afterwards. I have had several crash and die if I repot, prune, style, and otherwise drastically stress the tree immediately after heavy blooming. A May-June, post flowering repotting should have ''mild'' root work done, not drastic root work. Mild would be less than one third of the root system being cut or removed. A trim around the edges and bottom, combing out the outer edges of the rootball would be considered mild, if you take less than a third of the roots system off.
So for your tree, I'd repot early spring, get the root system prepared for a life as bonsai. Prune to eliminate as many structural flaws as you can. Do all the radical work in one day, then use this summer to recover and grow it out. Take notes on when it initiates flower buds, take notes on its growth pattern to learn how it is different than a Satsuki.
Mine always bloomed heaviest in Autumn. It tended to be sparse in Spring. Once you know the rhythm you can adjust the timing of when to do the different azalea techniques. Once in the training pot, I would let it grow for at least 2018, probably 2019 too, just to let it settle in and for myself to get familiar with that particular plant's natural pattern of growth.