Using WD40 for cleaning (not lubricating..) I plan on cleaning/re-greasing my rear derailleur this weekend, something I've never done before. I watched a video on youtube.. the guy wiped it clean first, then used a spray lube (dry I assume?!) to clean it.. I don't have a dry spray lube and wondered if I could just use WD40 to clean it, and then apply grease.

So two questions really:


Should I use WD40 to clean the derailleur?
After cleaning, should I apply dry lube then grease or just grease? If I apply dry lube won't the grease just slide off?


Cheers,
John.
I clean my stuff with Simple Green. Rinse. Simple Green. Rinse until clean. 

I wouldn't use WD-40 if I were you though. I am not sure about the chemistry behind it but it is not a degreaser and there are plenty of other better options out there. 

Don't use grease either. Use a light oil. And remove the excess. I keep an old toothbrush around to brush in all of the oil to make sure I have all the little pieces coated then wipe off any excess. Anything dripping or about to form drips is excess. 

With grease and excess oil comes accumulation of dirt which is abrasive. By not using grease with is sticky and wiping excess oil you are effectively limiting the abrasives that stick to your chain. 

I am not super sure of what you mean by 'Dry Lube' I think you mean either a Teflon based lube or lube that is meant for dry conditions. I have used Teflon-based stuff before and it was a pink, waxy mess. That could just be the brand though. All the bike shops around me use Tri-Flo. Thats what I use. I have a small bottle that has lasted for years.