I have ordered trees from several different online stores. Brussel's is the only one I will never order from again. ( Lets just say that once they take your money they don't care about you anymore ).
I would recommend Joebonsai.com or Bonsaiboy.com, from Both these stores I got very nice bonsai in good, healthy condition.
The Satzuki Azalea likes acidic soil, so a blend of bark and pumice material should work well. Adjust the soil mix for your area ( If your area is hot and the soil drys out really fast, mix more organic material in the soil to help hold moisture longer ). What I try to get out of my soil mix is, during the hottest days of summer I want my soil to hold moisture all day and not dry out completely. Just make sure the soil drains freely.
The Azalea also will do best in a semi shady area or morning sun and afternoon shade, they don't like direct sun very long. And it is best to protect them from a constant wind.
The Juniper will live fine in the same type soil you use for the Azalea.(as long as it drains well)
Junipers like full sun( Mine live in morning and afternoon sun until around 2 in the afternoon then shade for the rest of the day)
On my outdoor trees I use a toothpick to help check when to water. Just stick the toothpick all the way to the bottom of the pot, or as far as it will reach( and you still can take it out), and leave it there. when you want to see how fast your soil is drying out, pull the toothpick out and look. I normally water when the first 1/4 to 1/2 inch of soil is dry.
When watering I like to use the submersion method about every other time I water, during spring time and summer.( soak the pot in a tub of water that just covers the top of the soil, let it sit in the tub of water till bubbles stop coming out of the soil ).
The rest of the time I pour water over the top of the soil until it runs out the drain holes in the bottom of the pot, let it drain awhile, then do it again. I do this a few times to make sure it is good and watered.