Measuring the Internal Resistance of an Electrolytic Capacitor
This is not a very good approach because the value of C is very poorly defined (often +80/-20% tolerance) and your external resistor will necessarily be much higher than the ESR of the capacitor, so I don't think you'll have any kind of reliable measurement. You'll be measuring the capacitance mostly, and what's left will be a small fraction of the resistance measurement. 

You should run the numbers yourself- determine the sensitivity to each value. 

If you measured with two different (say 2:1 or 5:1) relatively low value external resistors over exactly the same voltage change you might be able to get a good reading.