madvapes used to sell 510 connectors and eGo connectors too I think. Anyway, I'm all for scrounging connectors off
dead stuff. However, you can get those new too if you need them.
The other trick, is to solder a connector on each side of a tube...aka a test rig. Basically you break the center connector with two wires. This allows you to measure amps running
through it with the meter. Takes a male and female atty connector. Voltage would be measured by connecting the wires and measuring between + and ground. Amps are inline. Ohms are with no power and checked with the + wire and ground. Note the shell is a ground.
People often put clips on the wires. This is also so you could clip them together for voltage tests (but don't allow it to short to ground!)