This plugin requires you to manually add the trail every time you spawn. As Nanochip mentioned, cookies would be very helpful for this plugin. Cookie tutorial:
https://forums.alliedmods.net/showthread.php?t=228244
I tried to make this open to all players by editing the sourcecode, but it didn't work. Instead, I used Nanochip's advice and used sm_trails_override, which did work.
I was trying to change the source to allow anyone to use it. Out of curiosity, can someone tell me why it doesn't work if I change the original:
gCV_AdminsOnly = CreateConVar("sm_trails_adminsonly", "1", "Enable trails for admins only.", 0, true, 0.0, true, 1.0);
to this:
gCV_AdminsOnly = CreateConVar("sm_trails_adminsonly", "
0", "Enable trails for admins only.", 0, true, 0.0, true, 1.0);
I'm just trying to learn...