Personally, I'd go with a 4-wire measurement - or a home-brew equivalent.
Since I don't have a 4-wire meter, I'd go with the constant current source flowing through a reference resistor and then the DUT.
Measurements requiring accuracy:
* the reference resistor resistance (out of circuit)
* the voltage across the reference resistor (in circuit, constant current flowing)
* the voltage across the DUT (in circuit, constant current flowing)
Use Ohms Law to determine the resistance of the DUT - since the current through the two resistance is the same.
The actual value of the current is unimportant for the maths involved - but, as said above, be aware that it's not too much for the DUT ... AND that it is not enough to cause thermal variances in the resistors (either the reference or the DUT).
Edit: Actually, you don't really need a constant current source for this. Since this is a static topography, just make sure that the current doesn't vary between the two voltage measurements. I'd check VRref, VDUT, VRref, VDUT, VRref - and if they are consistent, that will be perfect.