Infinite Worlds and Cabal, how does their travel actually work?

[Boyboy180]

Recently I've been looking into using the Cabal in an IW game but the infinite worlds book doesn't actually explain enough of how they move from world to world without being lucky and finding a pre-made path.
Reading their original 3e book didn't help that much either.

So, I ask the following;
1. If it is possible to travel via the astral plane (As I have seen mentioned), how does the method work? (IE: Is it just "Plane shift to the astral, travel to the world you intend to go to and just... cast Plane shift again?)
2. If you can do that travel via the Astral, how far apart are different worlds? (Do you need to travel the length of the earth to get to the next one or is it something different)
3. What is the terrain in the Astral like between worlds? Would you need specialised transport?

And is there anything obvious I am missing? Things that would help me understand their method of world jumping?

PS: Are Cabal characters assumed to be able to use their magic on any world with mana they visit or do they lose access to it if the world doesn't naturally support that type of magic/mana? (Things like using the base magic system in a Monster Hunter setting instead of RPM)