You don’t need to use Silver Solder for ordinary electrical wiring as strength is not really an issue.
Silver solder is useful for soldering things that require mechanical strength such as applying detail parts to a brass locomotive. If soldered correctly then ordinary resin core solder is sufficient.
When I was being taught “High Reliability Hand Soldering” the instructor said there are three rules to good soldering:-
Rule 1: Clean, Rule 2: Clean, Rule 3: Clean
While this is probably extreme for Model Railway use it is something to keep in mind.
When I solder wire to track I clean the side of the rail with an ink eraser (not pencil eraser) and a drop of flux.
I use a small, cheap 15-30 watt pencil type iron. There is no need for an expensive temperature controlled iron and definitely not a butane type. I doubt anyone could solder a wire to a rail with a butane type without damaging the plastic ties.
The important thing with soldering wire to rail is to tin both the rail and the wire first.
Remember that you do not need a huge blob of solder on the rail to get a good strong connection, the tinning is sufficient.
Just place the straight wire on the tinned section of rail and touch the rail and wire at the same time for a second and it is done. The solder should be shiny and flat after it cools, if not you should reheat.
Do not allow the wire to move while the solder cools or the joint will crystalize and look rough and grey.
Just try it and you will find out it is not hard,