My advice is to practice, practice, practice. If you do it a fewe times, you will get a feel for it and not melt ties, even without removing them or subbing out PCB ties. The installing PCB ties adds some interesting other ways to attach the feeder wire - but you do have to solder the rail to the PCB tie and at some point there will be a PCB tie next to a palstic one - unless you handlay all you track on PCB ties (my attempts to hand lay turnouts failed from not getting good frogs and point blades - so hand laying sone straight/curved track is something I may do just for a small part of my layout - seeing as I have a huge bag of ties and all the necessary tools).
What Overmod suggest is what drives me nuts in many MR videos - because usually what they show is 60/40 solder being used in that manner, which is NOT eutectic. Using a eutectic solder like 63/37 or some other alloy greatly lessens the chances of getting a cold joint when you aren't first forming a solid mechanical connection and happen to be a bit shakey like David Popp. I'm all for giving yourself a challanege in order to improve skills, but at some point it becomes a case of use the right tool for the right job.
ANd those who are just working up to soldering skills - notice a recurring theme in every post frome those of use who have been doing this a long time? CLEAN TIP. My soldering station came with the bronze wool cleaner, and like the station itself, I can't believe I didn't get one years before I did (though they used to be a lot more expensive - so as a kid I made do with the 60 watt fixed heat iron we had, when the 250 watt gun was too big. That iron had a relatively massive tip, too - but I built a computer kit without melting anything or ruining the PCB, and 40+ years later I still have ot and it still works.
But the key is and always has been cleanliness. A bright shiny ti transfers heat quickly. A dull oxidized one (I've seen people trying to solder with nearly black tips) means you have to hold the tip on the place you are trying to solder for a long time before it reaches solder melting temperature. In the meantime, that heat is conducting through the metal you are trying to solder and heating up the whole thing. If it's a piece of rail - you will hit plastic tie melting heat before you hit solder melting heat. With a clean tip, the point of contact heats up very quickly, before the heat can conduct over to those plastic ties and melt them.
Just NEVER EVER use an abrasive on a soldering iton tip in an attempt to make it shiny. The shiny comes from metal plating. Tips are usually solid copper plated over - copper ozidized FAST. Using sandpaper or a file just strips the palting off and that tip is effectively now useless. Back in the bad old days of those giant soldering irons, or even the type that you heated in a gas flame, they weren't palted, so people were constantly filing the tip to get a clean spot. I even recall one of those old MR Kinks column ideas that showed filing the soldering iron tip to a specific shape for special jobs.
The bronze wool works great for cleaning between joints. Once ina while, the use of a tip tinner (sal ammoniac) cleans things off completely, but eventually it does wear the tip, so this isn;t something you should need to do every time you use the soldering iron. Lastly, when finished for the day, melt a blob of solder on the tip so when the iron cools, the tip is protected by a blob of solder. Next time you turn it on, when that melts, a fews pokes in teh bronze wool and you will have a nice shiny tip ready to solder. ANd when installing a new tip - first thing to do when heating it up is to melt solder on it - like putting sold on a bare wire, this is also called 'tinning'.
It seems like there is a lot to read, but I've been very repetitive. Clean, clean, clean. That's the overall watchword. And practice. You will quickly get the hang of this.
--Randy