The easiest way to tin wire is to hold down the soldering iron using something heavy (like the stand, or a trusty pair of pliers):
Then simply touch the wire and the solder to the iron simultaneously and draw the wire across the iron towards the cut end. Remember to leave that thermal gap (of approx 2mm) between the tinning and the insulation, or 80s "sodderman" will come and find you. (Not so important with PFTE wire as it's pretty much impossible to melt.)
And here is an example of a nicely tinned wire (the OT centre tap). Note the insulation gap at the bottom.