Hey Paul be very careful with what you spray into the jacks. Make sure it evaporates and doesn't leave an oil residue as this will just attract dust, and if you're anywhere near the coast the dust will absorb the salinity that's in the air and then that's the start of corrosion.
Theoretically the normalling contacts should be self cleaning. They are designed to have a wiping action when you remove the plug and the contacts close. Always try inserting a plug in and out of the jack 10 to 20 times as this often will self clean the normalling contacts.
http://www.redco.com/Vertigo-TT-BURNISHER.html
very sparingly for regular contact points.
A burnishing tool should only be used when the patchbay or a jack has not been used for a some time.
This is usually the case with a console that's been in storage for an extended time.
In general use the repeated insertion and removal of the plug should clean the jack by it's wiping action.
If you're going to use a burnish tool, insert it into the jack and give it 2 full rotations then move onto the next jack. If this doesn't remedy the problem you may need to retension the springs.
The only "fault" I have had is from engineers smoking while patching and melting the sheath!
...and dropping ash into the bay.
If you regularly clean the patchcord plugs, keep food, liquids and cigarettes away from the patchbay, vacuum it once a week and remove patchcords and by grabbing the plug and not the cord, then you shouldn't have too many problems with it.
If the studio is near the coast and the console has a horizontally mounted patchbay then I'd highly recommend covering the bay when it's not in use.
Finally if you're having repeated problems with crackling and intermittent connections, then you may have a patchbay that has the jacks mounted on a printed circuit board.
This type of patchbay is notorious for having problems due to hairline fractures where the jacks are soldered to the PCB. There were quite a few manufactures in the 80's that used this type of patchbay... Soundworkshops, Soundcraft, etc. The problem was only made worse by the engineer jiggling the plug around trying to get a better connection.
If you have one of these consoles and it's suffering this problem, let me know and I'll do a post on how to repair it. Mind you, it's not a job for the faint hearted!
Hope this helps.