You can clean your Bug A Salt Gun by soaking it in hot water. This will break down the salt build up in the gun. Let it dry completely before reloading with salt.
Per the manufacturter of the the Bug-A-Salt Fly U Bug Salt Gun, it may "sting" scorpions somewhat, but would most likely not have enough power to completely kill them down due to their hard shell.
The manufacturer states that nothing other than salt can be used with the Bug-A-Salt gun.
The Bug-A-Salt Fly and Bug Salt Gun only uses regular table salt for its ammunition. You can view a video of how to load and use the Bug-a-Salt here.
The Bug-A-Salt Fly & Bug Salt Gun - Camofly 2.0 is designed to be used indoors and out. If there are any salt granules left behind, they can just be wiped up.