I'm not Tony and I seldom see him post on the forum, at least not recently. He does still maintain the forum and "pays the bills", so certainly is still supportive in that way.
I don't have a DX8 or any other Spectrum transmitter since I chose to go with Futaba... but the questions you ask are generic enough in an electrical and mechanical direction that I can point you in the direction. I'm also ignoring the other post you made in another thread, since it is redundant to post the same type of question twice, it won't get you answered any quicker.
With the exceptions of worn out or bad gimbal rheostats ( the electronic portion of the gimbals )... cleaning is easy. Just spray your cleaner into any opening they have ( the rheostats, not the gimbals ) and move them back and forth, they in this case are the sticks since they move the posts going into the rheostats. I'll repeat that process a few times and then test to make sure they aren't "noisy" and I get a stable signal from them.
The DX8 have a "million" revisions since it was first released to address issues that have been seen with the transmitter since it was released. One fix that Horizon Hobby was doing to some early on with noisy signals was to directly solder the wires where they had a white connector going to the main board. In other words, where the users thought they had bad rheostats on the gimbals was actually being caused by a bad cable connection. Testing this as a possible cause should be easy by first just cleaning the connector points and second by applying some light pressure to the connector while testing. Cables and connectors are the bane of all electronics everywhere so should always be one of the first things to check.
The DX8's also had some revisions with known bad gimbals that just had to be replaced. They used to have a post on their website about this but I was unable to find it. There were around 10-ish revisions that had that issue at the time I read about it, more may have been found later and if so, would explain why I couldn't find the original that I'd seen posted about since they would have updated the posting. If this is being caused by a defective or even just a worn out gimbal rheostat, no amount of cleaning can fix it. The only fix is to replace the gimbal in this case. You can ask Horizon Hobby about this directly without it costing you for more specific info about it, they will likely ask for your serial number or PID which should be located in your battery box on the transmitter so they can look up the info specific to your revision you have. Of course, they won't be able to say if yours is bad but they can tell you if it was on a recall list as being a known defective issue with certain revisions.
Since you posted in the other thread about lubes... As for the physical gimbals and any lubrication they need... I recommend a grease type that will not run off like a liquid. I prefer one with teflon in it but silicon based ones are fine as well. Just don't use much, it won't take a lot to cover the surfaces and provide a smooth action.
