If you want to use the "back up the toad until the arms lock" method, and only one arm locks, a velcro strap or bungee cord will let you hold down the locked arm release so that you can pull the toad forward, adjust the toad steering wheel, remove the velcro strap or bungee, and try again. Even if you have a helper, that person should not be between the toad and the coach when you are moving the toad forward.
After a few times hooking up, it will be easy.
I keep the velcro strap on the body of the tow bar for ease of access.
Fred