Checking wire continuity or component resistance is a simple task. The majority of avionics/electrical troubleshooting requires the ability to decipher meter readings correctly.
Troubleshooting aircraft systems requires access to plug and rack pins. Having a set of different size test leads is essential. Safety wire is not a practical tool for testing circuits.
I use test leads that I made from Amazon alligator clip jumper wires
. I cut them in half and crimped various size pins on them. I use heat shrink tubing to protect all but the working end of the pin.
I ground down the tips of my meter test leads about ¼" to accommodate the alligator clips. When I hook up to the meter lead, I push the rubber of the clip over the plastic of the lead. This prevents inadvertent grounding of the alligator clip on metal. It's always nice to see that split second of flash and spark, then be left wondering what you just fried.
I like to have at least two each male and female sizes in the red (20) and blue (16) gauge pins. Digital computers use smaller pins in the 24-26 gauge range. The males in this range are easier to obtain because the rack plugs use them. The females are not easy to find, they are on the computer (LRU) plugs. The component shops have them, but line mechanics do not normally have access to these. The problem is, the females are needed to get into the rack pins for troubleshooting. If you find any females in this smaller size, take care of them.
If a plug with bent male pins is found, try using a female pin to straighten them out. It is a lot easier than a screwdriver or needle nose pliers.
Just as a note: Always continuity check your test leads before using them. They do wear out and go open. I've been caught many-a-time using bad or on the fringe test leads, it can cost you hours of work.