I have the magnetic device, the clamp style, and the "remove the liner and screw in" types. All work with some limitations, as noted. The magnetic type can be bumped and moved, causing leaks. If careful, no problem. the clamp type can be wonky to get set up right. Both of those can occasionally leak where the tube joins the device, especially with hot water. The liner replacement types obviously can't work on guns where the liner can't come out or is absent. The skewer in the hole, slosh and dump works as well, but I never thought it as thorough as the methods that pump water under some pressure. I have found some guns' barrel breech contours (outside shape) can effect the magnetic and clamp styles. It's a matter of finding what works best for each gun.
ADK Bigfoot