So I'm new to Trainz Railroad Sim 19. I used to play Trainz 12 back in the day.

I've been struggling to get a multiplayer session up with my friend and I was told that you can upload a .CDP file to the internet and then they download it.

What I am trying to do is the following:
1. Edit a payware session Ex: Coal Country and use trains / cars in other payware materials such as using ATSF locomotives / BN brand. (Not using any 3rd Party!!).
2. Upload it without any errors. These are the ones i'm getting when I get a response from DLS.

An Error Occured with <kuid:495739:100057> TheCHcuky's Session
<kuid:495739:100057> : Asset <kuid:495739:100057> is a multiplayer session but has dependencies that are not builtin and not available on the Download Station (<kuid:495739:100056>).

3. Give this to a friend to play with the ATSF locomotives / BN brands instead of the built in payware marital.

So with all that said I have a few questions.
1. Are you able to somehow edit a Payware Session ex: Coal Country, and put in your own custom trains into it such as each train car individually instead of the pre-made trains, or do you have to make Pre-Made trains and built it into the session you want to edit?
2. Are you able to use other brands of trains in other and place them individually?
3. Are you able to add other brands and built them into another Payware session to avoid the errors?
4. Are you able to make custom pre-made trains from payware sessions and save them and use them for different payware sessions when editing them for a multiplayer session. (ex: Instead of individually placeing each brand or train make a custom on and use the second option to the right in the Surveyor?).

5. Is their a shortcut that I'm just not seeing hear?