I have 2 questions.

1 is probably a common one, but I can't find the answer. Unlike other games I've played, there's no help section in Heroes (or maybe I just don't have it).
The point is: how do you move only part of the troops to garrisons and other mines? For example, there's a scenario where you need to bring a hero with a certain number of units to a tent. I've calculated the number, but how do I make sure there are exactly that many? Or, if I want to leave, say, 2 dragons in a garrison, but I have 5 of them?

2. Why does Faidaen need phoenixes if they're useless (in the last mission)? Wouldn't it be easier to just build up the army?