there should be no continuity between the large threaded "batt" stud and the mini bolt on brown wire "solenoid" terminal. Same thing on the large/small starter terminals (no continuity). It is a good precaution to pull a batt cable before switching the meter to ohms. EDIT Which I'm sure you will (just a caveat) take off the main cable/brown wire either at the starter or at the SR before testing either component cuz with the wires still connected, if one device has continuity both em at their terminals will show continuity. holler (with) what you find out.
possibly a flashlight battery/flashlight bulb & several jumper wires with alligator clips. Likely you could take the top of a flashlight & jump from the center terminal of the top battery & the copper "slide" on the side that comes up from the lower battery negative bottom (whichever way is easiest for you with what you have). it wouldn't be near the same voltage but if it does show continuity then you know that that is the problem.
Do this first: Pull the yellow wire/terminal off of the "ign" terminal on the starter relay then hookup the battery & see if it cranks by itself like it is doing now (with key off).
Which wire?, the yellow one? The only way plugging it in could make it crank WO the key on is if the yellow wire/terminal is hot all the time which would point upstream toward the ign sw as opposed to the relay cuz the yellow wire is only hot when the key is turned all the way to "start". (I feel like I missed something).
Someone suggested tapping on the ralay with a screwdriver . I did that while I removed the yellow wire to test the cranking.after I hooked the yellow wire back up, everything works as it should. I guess the relay was stuck so I'm getting a new one.