Battery Drain - 2005 Ford Explorer Sporttrac

I think its a parasitic drain.  Battery is less than a year old.  Until yesterday
evening the truck was fine - leave it overnight, fine - leave it for hours while
on a hike, fine.  Last thing I did was wash the truck and now it dies quickly
when left off for mere hours.  I looked at the wiring harness at the back hitch
and it is corroded and rusty even with the cap on - thought maybe water got
into it.  I cleaned it with a brush only - no change.  

I got the truck going from a jump, ran it a few minutes, turned it off.  Dead
hours later.  Now there's nothing inside that I can see left on when I turn the
truck off.

I did it again, ran for a few minutes, turned it off.  This time I disconnected
the black from the battery and let it sit for hours.  Reconnected the black -
fired right up, no problem.  = Not the battery.

So now, see if this makes sense...I'll take my multimeter (though I dont know
how to use one, really), set it for the correct "range" so it reads a battery,
connect the red to red and the black to black, and I should get a measurment
even with the truck off = that'll be the parasitic drain.

Then I start pulling fuses with the truck off.  Go check the meter each time for
a change, and when the registered drain stops then thats the affected fuse.  
Then I find out what systems run through that fuse and start isolating those,
and so on.  

Sound right?