So far I've spred the ballast manually. It works but it is very time consuming. The main challenges are:
- Not putting too much ballast
- Removing ballast from the sleepers and tracks
I'm now trying two tools: a ballast spreader, and a 3D-printed "ballast vacuum".
Ballast spreader
This can be easily found online. The main issue was to control when to start spreading ballast. I used a small piece of cardboard and it worked perfectly:
From here, I further positioned the ballast with a finger going along the tracks.
Ballast vacuum
I found this on YouTube:
I followed the simple instructions for this Bexhill West's Ballast Vacuum:
This was quite successful and I will use this technic going forward. The only downside is that it removes a bit too much ballast on the sides, but this is actually the easier thing to fix.