Using PTFE spray on rear derailleur springs Have noticed that the rear derailleur springs and pulleys are picking up lots of road gunk.  I use a wax for the chain and as this breaks off I can see it getting stuck on the pulleys.

So after cleaning out the chain and rear derailleur with citrus degreaser can you use PTFE spray, as in WD40 400ml High Performance PTFE Lubricant on the rear derailleur spring.  PTFE is basically teflon, but does it then over coat the spring and restrict movement ?
You most certainly can use a PTFE spray after cleaning, but, I would use a high quality chain lube instead.  

I use this dry teflon lube on my drivetrain and use a precision applicator to lube my derailleurs after I clean the drivetrain.

Personally, I wouldn't use any WD40 branded lubricant on my bike.  Also, I'd recommend not using a spray type applicator to apply lubricant on small parts.  I like to use the precision applicator, i.e. the long, skinny straw, to be able to reach into all the pivots of the derailleurs and accurately apply the lube.  The spray can be messy and will often contaminate other parts of your bike, like rotors or brake tracks on your wheels.

The 'Dry' lube is nice because it doesn't pick up that much road grime in the derailleurs.