Another point on wiring a branch is leverage. A branch being wired needs four or five turns at least around the trunk if the branch is to be held in its new position. Ideally try to wire a branch up the trunk and out along another branch. When wiring is complete and the tree roughly bent into its new style it is time for repotting. When it comes to soil mixes everyone has their own ideas. Basically a soil wants to be fertile and free draining. I use crumbly garden soil, well rotted compost, river sand and crushed quartz in roughly equal amounts for junipers with a bit of this and that thrown in until it looks right.
The easiest way to mix the soil is to throw everything onto a plastic sheet on the ground and picking up two corners , toss the mixture towards the other end, then work it back again.
Now remove your tree from its pot or bag and clear the soil from around the base of the tree until the surface roots are exposed. Using a root hook carefully rake the soil from the sides and half to two thirds off the bottom, trim off whatever hangs out. Now place your tree in the pot and position it so that it is balanced about one third of the way across the pot and just behind the centre line. The heaviest branch should project towards the wider side of the pot. Place fresh soil in the pot and using a potting stick or chop stick work the soil into the spaces between the roots. Check the angle of the tree and position of the branches and adjust if necessary. Stand the plant in a container on water for half an hour so that all air bubbles are displaced.
Place the newly potted tree in a sheltered position for a week or two, then move it into full sun which will, along with pinching, help keep the new growth compact.