In my experience any knife, electric or otherwise, creates the dreaded "dribbles". The hot wire is the only real way to avoid this.
I have cut some styrofoam using one of the gun style soldering irons. Take some copper wire, guage will depend on your gun, 12g worked for me, and make a longer soldering tip. Unscrew the stock one and install your special tip. Do not squeeze the wire of the tip too close together, electicity takes the shortest path, and the tip will not be hot. Crude, but it worked.
2002 35R Southwind, W22 8.1L Vortec UltraPower, 19.5' wheels
Toad: Wrangler, lifted and on 35" tires