I have an iMac G5 keyboard with key action that is not as smooth as it
should be. I've cleaned it, thoroughly, but some keys still feel a bit
tight. I don't think it was ever the best keybiard in the world...

It's the type in which each key spring is a little cup of what I think
is silicone rubber.

I want to lubricate the keys. What would be the best kind of lubricant -
a dry power, or a silicone grease spray?

Silicone grease from a tube in the past wasn't very effective - it
collected a lot of dust which made the keyboard stickier.

Maplin offers:

Silicone grease with PTFE:
http://www.maplin.co.uk/Module.aspx?ModuleNo=30030&&source=14&doy=3m1

Multipurpose silicone grease:
http://www.maplin.co.uk/Module.aspx?ModuleNo=29006&&source=14&doy=3m1

I can't find a dry power spray I used to use though.

Thanks for any suggestions.

Daniele