I have new 3/4 wood down and i am needing to trim the transition edges before i put the transition pieces down....we do not want to use T moulding because there is a height diff between wood and tile. I only get one chance at the cut- approx 18 feet total of transition cuts. what is the best way to do this.

I forgot to mention- i have a freund trim blade/ circular saw/ i also have a rotozip. I purchased an aluminum guide to keep the cut straight.

I am not sure I am reading the question correctly, but if I am, then you have already gone past the "best" way to do this. You should have installed the transition first and fitted the floor boards to it.Alternatively, a temporary stop block and fit to that. Then your permanent transition would have dropped in place.
I believe that, using the tools you have, and applying care and skill to the cut(s), you can still achieve a clean straight edge.

thanks for help dennis. would have liked to have installed in this fashion, but threshold was backordered and had limited amount of time to get main floor in.