To modify the Gertboard, I added a 4.7k pulldown resistor to each of the lower (lower according to the schematics above) buffers to keep their LEDs normally off and to provide anti-static protection. 100k pullup resistors were added to each upper (upper according to the schematics above) buffers for anti-static protection.
The modifications were made by soldering surface mount resistors to the underside of the Gertboard. The resistors were of the 1206 size - 0.12" x 0.07" x 0.02" thick. These are about the smallest parts I can solder by hand. The 4.7k resistors (pulldowns to lower buffers) are soldered between adjacent pins of J10. This was fairly easy as the distance between these pins was 0.1". Refer to the photograph above this paragraph. You can see these resistors along the bottom edge.
Soldering the 100k resistors was a little more difficult since this was done at the ICs pins themselves. A copper wire was soldered to pins 20 of the ICs. The resistors were soldered between these copper wires and pins 2, 4, 6, and 8 of the ICs. You can see these connections in the photograph above. I suggest you use the single strand, 30 AWG, wire-wrap wire for this purpose. This is available from Sparkfun for about $9 for 100ft.
If you are using any of the three switches on the Gertboard, the 100K resistors are sufficient to pull the level up to 3.3V when the switch is not pressed. Therefore, it is not necessary to use the Raspberry Pi's internal pull-ups.