I think your order of introduction, and more importantly rate of introduction will depend largely on two things, in my opinion:
1. The "life support" system for the tank, and the contingencies available to you should things not work out as planned
2. The size of the fish
Since you largely know most of the details which will effect these variables, then you are half way there. You have the fish in "holding tanks" already - which means to say you good mature filters and water already, and you have the facilities to isolate ALL of them, if need be.
So this largely lets the question of how you are looking to set up the "system". i.e. is it fowlr or something like wet/dry filter? Skimmer? How mature will the system be, or indeed the components that make it up?
I think the ideal solution is to introduce everything at the same time...... or similar to the steps set out in JazzZero's reply..... but the details of the system will gouvern how feasible that is, in my view.....