Here is one way to set up this systerm.
- Create a low resolution nCloth and simulate the large-scale motion. I will call that low resolution nCloth mesh "cloth_L0"
- Cache cloth_L0
- Smooth cloth_L0 using Mesh > Smooth. Be careful of having too many divisions as very high subdivision levels will cause significant slowing down of the simulation. I usually choose 1 to start with and then repeat the process if I need more detail.
- Export the smoothed cloth_L0 as Alembic using Pipeline Cache > Alembic Cache > Export Selected to Alembic. If you want to preserve UVs, remember to tick the check box in the options box.
- Import the Alembic file bac in to your scene. Rename that imported mesh as "Alembic_Import_L1"
- Duplicate Alembic_Import_L1. Rename the duplicate "cloth_L1"
- Create an nCloth from cloth_L1
- Select cloth_L1 and shift-select Alembic_Import_L1, then create an Attract to Matching Mesh constraint using nConstraint > Attract to Matching Mesh
- In the constraint, choose a Dropoff Distance that makes sense in your scene. You want cloth_L1 to be able to deviate just enough from Alembic_Import_L1 to add some good detail, but not so much that it no longer the follows the large scale motion of the original simulation.
- In the Strength Dropoff ramp, create a profile that has a value of 0 in the left and 1 on the right. An exponential curve will work well.
- Tune the forces acting on cloth_L1 to give a variation over the movement of cloth_L0.
In my example above I have chosen to use a division level of 2 because the original mesh was so low resolution I knew I would require quite a lot more resolution to get more detail.