In Boris Title Studio, have a look at Shaders (from the top tool bar) / Deformers / Mesh_Shatter to see if this effect is close to what you are looking for. The Control Window provides a lot of options for this effect.

This effect is in Title Studio 11 … I'm not sure about version 10.

Thanks! I don't have AE, but the Mesh_Shatter in Boris Title Studio works passably well.
I also tried using a transition from NBFX ("Lotsa Leaves"); this works, but has such a low limit on how finely the "leaves" can be represented, it's just not up to the task.

I think the Mesh_Shatter could be perfect if I could figure out how to make the particles move sideways instead of up/down ("Gravity" in the BCC settings).

with Boris you can try this = get yourself some footage like this

render it out to an image sequence.

in Boris on your text/image right click = distortion filter 2D particles. in your control window = soft explosion > scatter wipe tab tick custom gradient on the timeline > on the TL select the image sequence and key the explosion time properties. if you have boris blue use the standard mesh shatter but with the effect on the text/image

@ IAM4UK = "I think the Mesh_Shatter could be perfect if I could figure out how to make the particles move sideways instead of up/down" = in attributes . velocity mode select left -right

If you want to do it old school. Get some light colored sand or a lot of salt/sugar. Lay an even layer on a black card. Hang camera above the layer as wide as you want, then blow the sand/'salt/sugar in some way to make it look wind blown. (fan, breath etc). The use this as an alpha luma key to replace the sand with your footage over your background. (if it sounds silly remember the first star fields in Star Wars were holes in a black card shot at different zoom speeds.)

Thank you all for these responses. This forum is very valuable, and you illustrate why that is so.

in attributes . velocity mode select left -right

 

I see Mesh_Shatter / Transformations / Material Attributes / Velocity Mode ... but there are no settings like left-right. Is there somewhere else I should be looking?

Under Material Attributes, the Scatter Wipe Mode has a drop-down box that provides lots of direction options including left to right.

Under Material Attributes, the Scatter Wipe Mode has a drop-down box that provides lots of direction options including left to right.

Scatter Wipe Mode is present, but has no options, no range, and no drop-down box. My version of BCC Title Studio is 10.xxx, so maybe that's why it lacks that capability.

Make sure that you've got the Mesh_Shatter FX highlighted in the track header (the panel just to the left of the timeline) and that you have Control Window activated via the Window menu in the Tool Bar at the top of the Title Studio window.

If the Mesh_Shatter FX is not highlighted in the track header, the controls for that FX will not appear in the Control Window.

Thanks, Dexcon. The key thing I was missing was the Control Window; I was trying to adjust in the lower portion (timeline, left side).

Meanwhile, I found that BCC Extruded Text seemed to give me same/better results with an easier interface, all options clearly available.

here is a quick example of using the lighter values of the clip to shatter the text like dust . this is only with fx 2D particle. as i said above you can use the shatter and the particle because the shatter bits are still very big.

Thanks for all the great advice and tips!
Here's a rendering of what I came up with in my experimenting. I used Boris BCC Mesh Shatter fx with the finest mesh size and Gravity set to 0.
https://vimeo.com/276622786