Subsidiaries Question

I’ve never used subsidiaries, but am wanting to start (to save on extra maintenance costs).

First, how does the money flow work? I know there is initial seed money, but can the holding keep sending money to the subsidiary? Can the subsidiary send money back?

Also, are subsidiaries allowed to IL with other players or only the holding company?

Subs can IL with other players as well as the other airlines in the same holding. The only way to move money around after the initial founding is by owning an aircraft, then sale it to one then transfer it back. Repeating that until you moved the amount you want.