Siphoning carbonated beer

I recently tried the closed-system pressurized fermentation technique outlined in this thread. I didn't have a Sanke keg big enough to ferment my 5.5gal batch, so I instead split the batch between two cornies and tee'd the spunding valve to both.

My problem comes in that there is a yeast cake on the bottom of one of the corny fermenters that is plugging my dip tube and/or poppet valve. I had intended to counter-pressure transfer the beer through a filter to the serving keg, but with the dip tube clogged, there's no way to empty that fermenter under pressure.

So... I've decided that I need to rack the beer to the serving keg. The problem is that the beer is carbonated with ~2vol of CO2. Attempts at using my autosiphon fail because the beer offgasses enough to break the siphon during transfer.

Any tips/tricks to making this work? Would using larger tubing and no autosiphon be less likely to break siphon? How can I keep the CO2 from coming out of solution, or do I have to decarb completely?

How about shortening a dip tube and then counter pressure transfer?

hook up to CO2, hook up a picnic tap, pour one pint to clear the trub. Purge the serving keg with CO2 by opening the pressure valve and connecting the CO2 to it for like 10 seconds. Take off the picnic tap, connect out to the out of your serving keg. (make a short clear tube with an out connector at both ends). This will fill you serving keg from the bottom, disturbing the beer as little as possible. when you see air in the transfer tube, stop.