 For soldering rail to PC ties and doing it quickly enough that I don't melt the plastic ties in the Central Valley tie strips, I use liquid rosin flux, 20 thousand rosin core solder, and a well or 35 watt soldering iron with a 93 thousand screwdriver tip. I like the screwdriver tip because it closely matches the width of the PC ties and the flat bladed end allows full surface contact and near instant heat transfer to the entire width of the joint. I apply rosin flux to the PC tie with a small paintbrush. I clean the soldering iron tip on a damp paper towel, load the tip up with a bead of rosin core solder, and touch the tip to the fluxed PC tie and rail side. The solder flows easily and rapidly into the joint and I only need to apply the tip to the area for about one second. Fast enough the plastic ties nearby are never affected. That's all there is to it. In a few minutes the rail is solidly soldered to the PC ties and is perfectly engaged thanks to the self gauging slots and the plastic ties.