Here's a BETTER option guys and gals  

Do the 5 gal bucket with a water cooler bottle funnel into the fuel jar option.  Works WAY better. 

Cut off the bottom of a 5 gal water cooler bottle so it's a giant funnel (they fit perfectly into a 5 gal bucket).  Set your fuel sample jar down into the middle of the 5 gal bucket, now put the giant funnel down in (it fits perfectly into the jar).  Now you don't have to line up the bucket/jar perfectly under the fuel drain... you have an 18 inch wide funnel!

If you're in a really windy location, you can screw the 5 gal bucket onto a self-made wooden box to raise it so the height of the bucket/funnel are just an inch below the belly so the wind doesn't spray it everywhere so bad (and the weight of the wooden box keeps the bucket from blowing around as well; granted, you can just line the bottom of the bucket outside edges with a few rocks or whatever so it's heavy enough to not be blown over as well).  

Got this idea from a cool foreign utility guy.  Works awesome.  SO much quicker and you're not putting a precarious glass jar on a stick and having to aim it and keep from spilling it.