Irene,
These are rambling thoughts concerning how I grow Satsuki.
Azaleas like acidic soil, so watch your soil ingredients for pH.
I use my basic soil mix and 50% Kanuma. It works well for me in North Carolina. Echoing what Bill S said, they like to be consistently moist. That is my main reason for using Kanuma, it retains moisture and seems to help distribute it thoughout the soil mass.
I fertilize them with regular old miracle grow, just like everything else I grow. I have seen no ill effects.
They are basally dominant. Leave more leaves to the top of the tree than you would with other species. Prune harder on the lower branches than you would with other species.
I repot as blooming reaches it's peak, or just after. I also prune at the same time. I understand this may be old fashioned technique, but it works here for me. (I have a long growing season and mild winter. That might help make this successful for me.) My understanding is that there is a halt in new root development during flowering, and then sort of a second spring of increased root growth soon after flowering that helps the tree recover from repotting.
During post flowering pruning, I remove all ovaries and selectively prune excess branching as azalea tend to form whorled growth with 3-5 branches commonly emerging just behind the spent flower buds. After new growth emerges post pruning, you will probably want to go back over the tree to eliminate new whorled growth.
I try to remove blooms as they form over the summer on trees I am growing out. Hurts to do it, but helps to increase the amount of energy spent on growth.
Healthy satsuki bud agressively after hard pruning (remembering basal dominance). They bud from old wood readily as well.
Satsuki bloom off of last years growth, although in milder climates, buds can develop late winter and bloom that spring. Typically, the later you prune this year, the less flowers nest year.
Satsuki can tolerate more sun than other azalea.
Keeping open flowers out of rain and limiting wetting flowers during watering will help the flowers last longer.
I like to use a slightly larger, deeper pot than I might for other species. Helps with the even moisture thing.
They have very fine roots, but typically throw out lot's of them, so I agressively prune roots as needed. You might want to go easy at first. They develop excellent nebari even though they produce fine roots.
Watch for lacebug. It is the main pest I have. They live and breed under azalea leaves, sucking the leaf juices out, leaving lot's of small areas with out green. Leaf looks kind of bleached. If you turn the leaf over, you will see small black dots. This is sometimes eggs, young or turds. Systemic insecticides work well.
I do not have any experience growing the Encore varieties. I don't know that the above will work with Encore (especially the repotting due to repeat blooming) azaleas. I only own 2, one is being grown out in a container for the third year before heading to the landscape and the second is probably headed for bonsai training come spring (purchased last fall and no work done on it yet). Enjoy learning on them.
I find them easier to grow than many other species, but North Carolina is an excellent place to grow azalea in the landscape, and that seems to translate to them growing well as bonsai. I don't know how azalea do where you live, but I find them incredibly rewarding to grow as bonsai and wish you great success with yours!
I am sure there is more to say, but that is what I could think of.
Regards,
Martin