Once the Z-Scale track is in place, it needs little attention except for periodic cleaning. Based upon many years of experience and based upon the advice from others who are more experienced, you should simply clean your track periodically with a soft cloth and little more. Track cleaning fluids in general seem to attract more dirt after application. Abrasive materials of ANY sort scar the rails, creating more surfaces for the dirt to adhere to. Steel wool contributes an extra problem by leaving small shavings of metal which is electrically conductive. The magnets of passing locomotives pick up this conductive residue and it promptly shorts out the locomotive. In short, a soft clean cloth is all that is necessary.
In practice, the material on the track is likely to be the same material which accumulates on the wheels of the rolling stock. It’s a tasty amalgam of dust, locomotive oil, motor carbon brush residue, pet hair and whatever else is floating around the layout. An enclosed railroad is less likely to cause problems because it is isolated from many of the sources of problems. But, the oil and motor crud is still there. As described in locomotive maintenance, the stuff needs to be gently removed because it interferes with electricity flow to the locomotives.
There is a product called Rail-Zip which is supposed to enhance electrical conductivity, but I have no experience with the product. Likewise, you will hear some model railroaders vow that Wahl Hair Clipper Oil is a godsend. There is an electrical device on the market that ZAPS! the crud. Suit yourself, a clean cloth is simple and effective.
This does point out that you will need total access to the track on your railroad. The more inaccessible a segment of track is, the more likely that you are to have trouble there. If it’s too late for that, you can fashion a cleaning pad on a stick and probably reach that hard to access spot.
In practice, the overhead wire does not seem to be particularly prone to becoming dirty, since the conducting surface is on the underside of the wire. Cleaning track with overhead catenary is a bit tedious. Märklin has manufactured a track cleaning car, the 8802: