Sorry if I sounded like a nob I did have a search myself and couldn't find it :)
This is what I do and is copied from a previous post. You need 3 keys. Assuming char 1 is the main btw.
Key1. char 2 strafe L/char 3 strafe L/char 4 strafe R/char 5 strafe R
Key2. char 3 strafe R/ char 5 strafe L
Key3. char 2 strafe R/char 4 strafe L