It isn't as hard as it sounds.

Place the bag of charcoal (this works for lump as well, so no worries)
on the grates of your pit, laying down. Orient the strings on one
side, the bottom of the bag on the other.

Take your chainsaw and cut the bag in two, being careful to keep as
much flying metal screaming around you from cutting you in two as
well. If you practice, you might get good enough to cut out some of
the grates as well, and if you are lucky you might have the charcoal
fall right where you need it. This is handy when grilling, but not
when you still need to load the firebox.

Now that the bag is open, call 911. You will no doubt need them
soon.

To start the fire before the EMTs arrive, pour premium (don't screw
with regular!) gas on the charcoal and the bag. I personally like one
gallon per ten pounds as a good ratio. Toss on a match. If it is
breezy, you can avoid your charcoal being blown out by doing this on a
wood deck with a wood cover, the lower and closer to the pit the
better to provide better protection.

If you are able, respond to the EMTs when they get to you. You should
be polite and ask them if they want a beer, and let them be the judge
of whether or not the fire department should be called as well. Let
the pros do their job!

OK. By now you might look like you were drug around behind a pickup
face down, and your house might be on fire. But don't worry. You
know how it's done now, and no one can take that away from you!

Oh, yeah... you should probably figure in a stipend to pay for your
upcoming divorce....

Robert