While I agree that you should do it right as said in my above post. This may help with troubleshooting, or if you are stranded. Replacing the glowplugs are the first priority. I had to do this once when stuck after having to change a filter, I NEVER said that this should be the way to NORMALLY start it. As far as getting rid of gas soaked rags goes....a match or soapy water in a bucket .
If any of his glow plugs are working you may just help him to find it by blowing up the gas in the cylinder.
If you must use some sort of starting fluid ... WD40 is a much better choice.
i had someone urge me to do this one time being very sincerly helpful... I refused, and trouble shot the issue to an IP with a bad ground... the gas probably would have kaboomed my engine, as it was hot at first and the glow plugs were working just fine!
If anything, a starting fluid/vapor is a last ditch... someone not stranded and having trouble using an volt/ohm meter is far from last ditch in my book...
break... break..
touch the leads of the volt meter together like Doghead said, they should read about 0. also make sure you have them plugged into the proper ports on the volt meter...
if that doesn't work, get a magazine like the national rifleman... look for a harbor freight coupon section, you'll find a volt meter you can keep in your truck for nothing if you get the right coupon.
edit to add: good glow plug bypass thread:
http://www.steelsoldiers.com/cucv/63366-glow-plug-pass-help.html