I also don't think the heater will do much for hours. If there's any place you can set it to heat the intake without melting wiring or tubing that would be a lot faster.
What caused the glow plug failure? With them all dead I think of a common failure like a relay or the ignition switch. If that's it you can jump from the battery to the wire that feeds the glow plugs.
For only a time or two it doesn't have to be any fancier than a heavy enough piece of jumper wire. Hold one against the starter cable terminal and stick the other into the connector of the relay socket going to the glow plugs or a glow plug contact if they're exposed.
What caused the glow plug failure? With them all dead I think of a common failure like a relay or the ignition switch. If that's it you can jump from the battery to the wire that feeds the glow plugs.
For only a time or two it doesn't have to be any fancier than a heavy enough piece of jumper wire. Hold one against the starter cable terminal and stick the other into the connector of the relay socket going to the glow plugs or a glow plug contact if they're exposed.