I have the 6.3 gal and don't let the oil-free fool you, it's quieter than most oil-lubed compressors. It won't run an impact but for brad nailers, filling tires, etc it's perfect. Super quiet for sure.
I haven't used them but I've seen lots of recommendations for Boggs Tool for cleaning and sharpening old files. Costs a buck or two per file depending on the length. http://www.boggstool.com/page5.html
Fluke is always a safe bet if he has the budget for it. If not, take a look at the Amprobe AM-270. I bought this one after a lot of research on eevblog.com.
You need to be aware of safety ratings when dealing with AC voltage. A $20 meter may be fine for 12V but you could be in for a surprise...
I have the same compressor. Needed something quiet for air nailers, filling tires, etc and I love it. It really is quiet compared to anything else I've heard and is perfect since my kids' bedrooms are above the garage. UPS busted up the box pretty bad so the company sent me a replacement unit...
I just found your awesome thread so apologies if you've already moved on from the dual color trays. If not (or for anyone else who wants to make them) the key to bonding HDPE is to flame treat the surfaces. HDPE is a low surface energy material like Teflon so almost nothing sticks to it. A flame...