My prep is to degrease the cable end with acetone then etch by dipping the end in muriatic acid. After drying the acid off I dip the end in electronics paste flux(what I have) then soldering with a 125 watt iron and flux core solder. This works really well with steel cables. The solder wicks in immediately, but not with the stainless cables. The stainless seems to be impervious to the acid etching step. I seem to have the best success at getting the solder to wick if I heat the cable just enough to get the solder to melt. Any hotter and the solder just rolls off. I may have to look into the silver solder and special flux.