The standard cable I have is coated on both sides it does not need anything over it.
The issues you will get from dust are:
- The camera lens gets covered and does not focus / twist so easily
- The USB and Ethernet ports get clogged
- The camera and screen connector get clogged
- The HDMI ports get clogged
- The SD card gets gritty when removed / inserted
After time, the chips on the board get hotter as the layers of dust settles on them or in any heat spreaders / fans you have.
- Regular maintenance with a can of air - let the Pi cool down first as the air gets cold very quick and you want to avoid thermal shock. Not that I have ever broken an adapter card from this...
- Use a good case - IP5x rated or above
The issue with the cases though are:
- Heat build up - fitting a filtered fan helps and good filters over the air entry / exit points
- Paths for cables
There was a kickstarter for a bird watching Pi case that was great but I've not been able to track on down for sales for months but the most extreme way is to put the Pi in mineral oil but I think that's a bit overkill to keep the dust away :)
- No the cable will be fine
- Keep the dust off the Pi and camera with regular maintenance