When your FLIP fluids are stepping

If your sim is looking steppy/choppy, it probably means the FLIP source emitter/colliders don't have substep information. To resolve this, use a Timeblend SOP & add a Trail SOP for good measure.

FLIP volume velocity field (again)

Create a VDB with desired turbulence/noise in whichever way you fancy. Make sure the vdb is called "vel". Keeps things neater..

Inside the FLIP autodopnetwork, use a Source Volume node to bring in your velocity vdb. Scale & Temperature can be ignored. Be sure to uncheck the velocity "mask" and set the volume operation to "add".

reliable(r) collision objects in FLIP

The deforming object shelf button serves most collision purposes, even for static objects (turn off use deforming objects) but sometimes it doesn't quite cut it.

Add a trail node, set to "calculate velocity" to your moving geometry.
Create a VDB from polygons node, setting the name of the volume to "collision" and add a point attribute at the bottom, choosing the "v" as the option. Name this "collisionvel". These names are defaults in Houdini.

In your FLIP sim dop-network, add a "volume source". Set the initialisation to "collision" and navigate the SOP path to the VDB you made earlier. Set the scale to -1, because that's how the maths work..and change the velocity to whatever you want..1 is probably sensible.
Finally plug the volume source into the "volume" connection tab of the Flip solver.

That should be it.

particle velocity to VDB fog/volume

particles, run a pointVop taking length of velocity and fit ranging them (min max to 0 and 1)
Plug new values into pscale.

VDB from particles, select fog, set minimum particle radius to 0.

should have a VDB mask ready for the faster parts of the sim.