I do the cut and solder too, to just add about 8" in the middle of the existing wire.
Scotchlocks work decently enough too, though you have to use them with larger sized wires as that's what they're made for (read the package). You can get them at any auto store, and they don't require solder or special tools to install.
I've even used the ones made for telephone wire, that you can get at Lowe's/Depot...they'll work on the smaller wires easily, and they're even filled with gel to stop corrosion in the joint.