I didn't acctually say you have to hit the reset botton, I said you will see activity on the multimeter at the very same time that you use to push the reset botton, when you upload a sketch.
Anyway what you have to do to track the DTR pin at your 'hacked cable':
1- Connect the 'hacked cable' to the breadboard/Arduino (as you do it for uploading a sketch)
2- Set the multimeter to the Voltage measuing range and ground the multimeter to 'hacked cable' and breadboard/Arduino.
3- Connect the other prob of multimeter (red) to one of the pads at the 'hacked cable' little PCB (find a pad that has voltage)
4- Now you have to upload a sketck, and look at your multimeter to see activity.
You have to repeat the 3 & 4, with all the pads on the 'hacked cable' little print board (PCB) one by one until you have find the DTR line.
To find the DTR pad at the 'hacked cable' look after the pad which is normally high (has voltag) and become low (for a few seconds) when you upload a sketch.
The Arduino reset pin is connected to the high (5V) thru a 10K resistor, and will be reset when connected to the ground(0V) That's why the DTR line is normally high and to reset the Arduino (when uploading a sketch) the DTR must become low (0V) for a few seconds at the right moment.
When you have find the DTR line, connect it to the reset pin with a 0.1uF capacitor serial in line (look at Arduino schematic)
I hope that could help you and write back about your progress.
PS. this is not a FTDI cable, rather a Prolific's PL2303 chip, the FTDI's chip which is on the Arduino board is FT232RL