Create a new composition 320x240, 4 sec. Name it "Text".
Create a new solid. Apply Effect>Text>Basic Text.
Click Edit Text.
Write your text. Choose your font and style.
My font is Georgia bold.
Set Size to 40.
You should now have something similar to this:
Create a new composition the same size and length as the previous, call it "wind".
Create a new solid mask it off and animate its position over about 2 seconds.
Your final result should look something like this:
Create another new composition, the same length as the other two. Name it "Sand".
Drag in "Text" then "Wind". Then create an Adjustment layer. And finally another copy of "Text".
Your Composition should look like this:
Apply Effect>Simulation>Particle Playground to the bottom "Text" layer.
Open the Cannon pulldown.
Set Particles per Second to 0.
Open the Layer Exploder pulldown.
Set Explode Layer to 4.Text.
Set Radius of New Particles to .50.
Set Velocity Dispersion to 0.
Open the Gravity pulldown.
Set Force to 0.
Open the Repel pulldown.
Set Force to 1.
Set Force Radius to 5.
Set Selection map to 3.Wind.
Now set a keyframe for Radius of New Particles at 0 and another at :5 value 0.
Make the last keyframe a hold keyframe.
Set this layer's in point to -5.
Note: If you plan to test your mask and do a lot of previews set the Radius of New Particles to a higher number and move the hold keyframe to frame 2. If you don't, render times just might drive you insane.
Turn off Visibility for Wind and set its in point to :5.
Add Effect>Blur and Sharpen>Fast Blur to Adjustment layer 1.
Set Blurriness to 2.
Then set the layer's TrkMat to Luma Inverted Matte "Text".
Set 1.Text's opacity to 65% and set the out point to 1:15.
Particle Playground is always very render intensive to use, but if you keep the amount of particles down to a minimum and keep the particle size as large as possible while testing, render time will be reasonable.