I did this job yesterday and I really appreciate the pics and tutorial. I thought I would post my experience to further help the next person who does this job.
1. I tried the drain cleaner method first.( liquid plumber gel) One side drained a little but later stopped up again as I was flushing it. The other side did nothing.
2.I tried both air pressure and water jet through the drain holes (when I finally found them) with no success. I also tried running a wire up from the bottom and never got very far. ( I'm posting a picture of the holes so you can find them but that method is not recommended.)
3. I finally decided to bite the bullet and clear the holes from the top and it really wasn't as hard as I imagined after reading this thread. I did the job by myself in about an hour and learned a few tricks. Here's the abridged version:
a) remove 2 armrest screws on one side
b)remove center panel behind it
c) 3 trim screws and rubber unhooked from rivet takes off the top panel to get to the hinge.
d) loosen the slotted hinge bolt behind the top panel.
e) remove 3 bolts on the back side of the hinge and leave its mounting plate fastened.
f) lift hinge about 2 inches and slide a block of wood under it to hold it up. I used a 2X2.
g) clear the hole with wire and hose stream and then reassemble.
h) repeat on side 2
I didn't remove the seat or unplug any wires and by doing it one side at a time it becomes a one man job. Also when you get the drains really cleared they make a whirlpool and sucking sound like your tub. Don't settle for less.