[FourPenguins]

I may be necromancing this thread, but I happen to be working with a 2008 festo solenoid at the moment and have a multimeter and supply handy.

The festo valve's solenoid coil, when connected directly to a 12v supply, will draw about 120 milliamps (.12A). It needs no resistor in series with it. The 2008 pneumatics system was wired as such:
[spike relay +] -> [solenoid +]
[spike relay -] -> [solenoid -]

The spike relay has incredibly low internal resistance, analogous to a switch. You can run your solenoid without any external resistor (and in fact you should). Its internal resistance is roughly equivalent to 100 ohms.

Your circuit (for manual actuation with a switch) should look like:
[power supply +] -> [switch] -> [solenoid +]
[power supply ground] -> [solenoid 1]