The reason why we repot in spring (or secondarily in early fall) is two-fold. First, it allows us to work around the extremes of the seasons. Second, it allows us to time our work for when our trees are most likely to recover based on their seasonal growth patterns. It might have been better to ask advice first than to do something and tell people about it afterwards. I am not judging - we have all done it - but when first starting out the most important rule to learn is patience. If you don't know, stop and ask. Short of your tree getting blown out of its pot in a windstorm, there is rarely anything in bonsai that can't wait an hour or two while you seek input. Otherwise you will just repeat the same mistakes that most of us have already made.
As far as rooting compounds go, they are designed to grow roots where none exist. Application of rooting hormone on existing roots either does nothing, or may actually harm roots if applied at a high enough concentration. Reserve your use of rooting hormone for cuttings, air-layers, or the base of a trunk where you are trying to get roots to grow where they don't currently grow. Do not use rooting compound when repotting a tree that already has roots.
The best way to get roots to strengthen (when they are already present) is to grow foliage mass. This does two things: first, it provides a lot of extra carbs to fuel growth, and second, it produces a lot of auxin (a plant hormone that tells a plant "yo I have a lot of foliage - time to make more roots!")
