It really depends on your goals. If you just want to get some trees in bonsai pots, you can usually make the transition from nursery container to bonsai pot in 2 years (two repottings with most species)
The good news is that for the types of plants you mentioned,
azaleas, probably your boxwood if it is healthy, and other trees with compact root systems, you might be able to plant in a slightly oversized bonsai container in a single transplanting. A lot depends on how the root system looks. This would not be a good thing to do with a pine.
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If you choose to do this, be sure to do the repotting work during the optimum repotting seasons, which would be around spring for your boxwood and early summer for the azalea.
If, on the other hand, the tree isn't very well developed, you might consider repotting into a large container or the ground to develop the trunk for a couple years, then back into a growing container for a couple more and wind up with a tree that will really knock their socks off.
My suggestion would be to do a little of both. Have some short term projects to keep you enthused and some long term ones to work on developing technique.