
I use the same set-up and do this all the time.
First connect a midi cable from the midiout of your soundinterface to the midi in on your 2500.
Then go into preferences in Logic, select midi, then click the Sync tab, in the bottom right corner of the box there's a (virtual) button that says MIDI Sync Project Settings, click this virtual button, this will bring up another box. Check the "Transmit Midi Clock" or "Transmit MTC" checkbox (whichever you want to use). Then under the checkbox select the appropriate midi out for your interface from the dropdown menu.
Then on your 2500 hit the mode button (it should flash) then the midi pad, select the sync tab, and set the 2500 to slave...either MTC or Midi clock (ensure that it's the same one you selected in Logic). That should do it. Logic should now control the 2500's time.
Then do as previously told above & route out using the 8 outputs, you'll most likely have to overdub, but the sync will keep the tracks aligned.
You might want to play with this a bit. I'm at work and am going purely from memory here.
*** Here's a helpful hint, put 4 blank bars at the beginning of your song in song mode on the 2500, this gives the computer and 2500 some time to initialize the syching. When using external midi time devices this is called chase time. Most products recommend 10 seconds of chase time. ***
Hope this is helpful for ya, best of luck...