On brake and throttle cables I have found it helpful to make a punch with an end boring to fit over the cable – just, and with a countersink. Mild steel will serve. Grip the cable in a soft-jaw vice, with the nipple above the jaws, leaving about 3-5mm between the nipple and the punch (depending on cable and nipple size), hold the punch dead in line and tap gently. With luck and/or skill the cable will open out into a tiny rosette. Keep tapping until the rosette expands to fill the nipple countersink, remove the punch and cut (or grind) the end of the cable and knock the ends down into the nest. Apply killed spirit, dip into molten solder, allow solder to set, and then into hot water where it can stay for a few minutes (to remove the flux).
And acetone or petrol is best to remove mineral oil – best done outside on a dry day.
Cheers, Tim