I don't solder straight track, but use jumpers instead. I also leave a gap at the joints that is the thickness of my NMRA guage (Yet one more use for that handy tool!).
On curves, I solder the first piece onto the end of the straight about a foot before the easement begins, then lay the track most of the way through that piece, making sure the sliding rail is on the outside of the curve. With about 6" unlayed I can then test fit and cut to length that piece and solder the next on, only removing a tie or two (save them, you need to shave off the spikeheads and slip them back in place later). Now you can continue laying out your curve until you get to 6" from the end of that piece, and just repeat the process.
Works for me, and the only thing I have to go back for is to slip in those few ties.