If you want to share custom skins, for example for an important league event, there are a couple of ways to do this:

Use skins transfer: this means all clients will have to connect as some point to transfer their skin to all users via the server (see Sharing with Skin Transfer for further info)
Create an update rfcmp that you distribute to your league-before hand that either gets manually installed or can be distributed via a workshop item.

In this guide we will be focusing on method 2: Creating an update rfcmp.

Before getting started: what is an rfcmp?

Simple put, an 'rfcmp' is what we call a 'package' file it contains the content you wish to install. This can be a track, a car, or even a custom HUD or UI.

For our purposes here, however, we don't need to get too into the details of what an rfcmp is, all you need to keep in mind is how to create it and then how to install and distribute it after.

The advantages of creating an update rfcmp are:

Clients don't have to show up early to an event just to make sure their skin gets transferred to all other clients
More control: the admin can check all skins and make sure no mistakes were made by the client in setting up their custom team
Less load on the server, no skins are transferred by the server itself and therefore it requires no extra bandwidth

This method does require a little extra work on the part of the admin, but once you get the hang of it should be relatively easy to keep doing.

Part 1: Setting up the VEH files

Step 1:

Make a folder (on your desktop) with the name of the car you want to create an update for.

Example: 'Bentley League Updates'

Step 2:

Collect all of your custom skin files inside 'Bentley League Updates' folder
- ```
<team-name>_region.JSON
```
- ```
<team-name>.dds
```
- ```
<team-name>WINDOWIN.dds
```

For this guide let's assume our car is called 'Studio397'
- ```
Studio397_region.JSON
```
- ```
Studio397.dds
```
- ```
Studio397WINDOWIN.dds
```

Step 3:

Open MAS2.exe → \Steam\steamapps\common\rFactor 2\Support\Tools
Double click on the MAS2.exe

Step 4:

Open the 'car-upgrade.mas' for the car you want to update (example Bentley)
Navigate to \Steam\steamapps\common\rFactor 2\Installed\Vehicles\Bentley_Continental_GT3_2017
Click and drag the file 'car-upgrade.mas' into the main window of the MAS tool
Select and highlight one of the VEH files and right click
Select 'extract' and save to 'Bentley League Updates' folder.

Step 5:

Rename the VEH <team-name>.veh
Using our example this would be Studio397.veh
This should be the same name as the corresponding DDS files

So now we have these files

Studio397.veh 
Studio397_region.JSON
Studio397.dds
Studio397WINDOWIN.dds

Step 6:

Open <team-name>.veh (Studio397.veh) in a text editor
change the following lines in the text

DefaultLivery="<team-name>.dds"
MaterialOverride="BentleyGT3_BaseMat.json"

Example:

DefaultLivery="Studio397.dds"
MaterialOverride="BentleyGT3_BaseMat.json"

IMPORTANT: Do NOT edit the line MaterialOverride!

Next edit the car details for your car:

Number=<my car number>
Team="<my team name>"
PitGroup="Group1"
Driver="<unique driver name>"
Description="Bentley Continental GT3 #<my car number>"
Engine="Bentley 4L V8"
Manufacturer="Bentley"
Classes="GT3, GT3_Bentley_Continental"

FullTeamName="Bentley"
TeamHeadquarters=""

Category="Bentley, Bentley Continental GT3"

Example:

Number=397
Team="Studio 397"
PitGroup="Group1"
Driver="Jefferson Bartholomew"
Description="Bentley Continental GT3 #397"
Engine="Bentley 4L V8"
Manufacturer="Bentley"
Classes="GT3, GT3_Bentley_Continental"

FullTeamName="Bentley"
TeamHeadquarters=""

Category="Bentley, Bentley Continental GT3"

Save and exit

Step 7

Repeat the above for all custom teams and make sure each team has it's own uniquely named VEH file.