Creating Heat with Resistors
Probably not the most robust way to go.  A single 1/4 W resistor has a thermal resistance to ambient of the order of 200°C/W.  So at 1/4W you get about 50°C.

Nichrome wire is much more practical and easier to control.  A 22 AWG piece of wire needs about 2.8A to reach 200°C.  You can size the current, heat needed, and space required to the necessary gauge of wire.  To heat the printer head you'll need to look at your losses in transferring heat vs time because you might need 350°C to get things started then back down to 260°C once everything is saturated.