Hi Mike

No Z specialist here (Märklin HO, C track), sorry.
Looking at the latest Noch website, they seem to focus on HO, TT and N
See their webpage here https://www.noch.de/modelleisenb...sbettungen-gleisschotter
There seems to be little choice for track beds for Z scale (look at ebay.de for Gleisbettung Spur Z)
I found this cork-bed for Z scale https://www.ebay.de/itm/31142945...D%7Ctkp%3ABk9SR-yth873YA
Otherwise, you have Rokuhan track or Merkur foam bed
Cheers
Jean

Hi Mike

Here is a link to Merkur and its Z gauge products.

https://www.merkur-styroplast.de...9631941dc4b3d78f9245bef2

Long time ago, I used Merkur products for N-gauge Rapido track and the result was fantastic:
- excellent aspect, true to life
- excellent approach for an elastic fixation of track: without nails or glue, track can be removed anytime, there are no stresses on very fragile Märklin Z track (DSS especially)
- excellent already fixed ballast preventing lose parts going into mechanism
- not so cheap but a good long term investment.

Cheers
Jean

If you have the full range of parts you could make some moulds with casting silicone (a 2 part mix).

Ideally you should use a vacuum pump to remove air from the mould. This is easy to do using a ridge container. I used a short section of large diameter acrylic tube so you can see the job (polished ends of tube), with thick plywood plates top and bottom. Rubber gasket to seal (rubber sheet).

I used a venturi powered by water mains pressure to remove the air bubbles. You only do this for a minute, the casting silicone fills the gaps. Then you have a top quality mould.

Once you have the mould, the easiest and less smelly is polyurethane casting mix poured into the mould. Then paint surface.

I did this decades ago, today it might be more time effective 3d printing the parts as long as you are capable of drawing the 3d files designed for 3d printing.

Failing that it is not that difficult doing ballast. Mask off key areas like critical areas of points. Spray with very fine water spray with a drop of detergent to make water wetter. Then drip PVA glue, slightly watered down with a drop or two of detergent, on the ballast. I used 3 colours of ballast to visually break up the overall appearance, so it didn't look to "plasticky".