This is for Adobe Photoshop users, but if you're patient enough, you can probably copy the concept with the pictures below as your guide.
1.
This is the pre-charge/blur frame. You may have a set of different frames before this one for your animation, but I'm limiting this tutorial to the actual blur effect.
2.
This frame is obviously the initiation of movement. For Photoshop (5.0 or newer) users, you'll be using a filter on a layer. Here are the steps:
---a. Copy the pre-charge/blur frame from step one onto a new layer.
---b. Highlight the copy layer you've just created in your Layers window.
---c. Now, on the top list of the Photoshop window (where File, Edit, etc. are), select "Filter" ---> "Stylize" ---> "Wind"
---d. The "Wind" window will pop up. From the "Method" list, select "Wind" and then select the appropriate direction that'll work for your animation.
3.
This is the last blur frame where the avi is even less visible than before, stepping at a speed completely beyond the capacity of normal human vision. Here are the steps for this one (which are similar to the previous but with one significant difference):
---a. Copy the pre-charge/blur frame from step one onto a new layer.
---b. Highlight the copy layer you've just created in your Layers window.
---c. Now, on the top list of the Photoshop window (where File, Edit, etc. are), select "Filter" ---> "Stylize" ---> "Wind"
---d. The "Wind" window will pop up. From the "Method" list, select "Blast" and then select the appropriate direction that'll work for your animation.
4.
The FINAL frame of that sequence would then be blank (white/black depending on what the rest of your animation is) since the avi has stepped out of view. How long to hold that blank frame is up to you.
And presto! You've flash-stepped your avi!
Don't have Photoshop? No problem. As you can tell from the guide pics above, all the Wind filter really does is cut your avi up in lines then move them aside in a jagged manner (and if you want to get fancy, you can do fades at the end of those "lines"). So in actuality, any paint program can create these frames. The only difference is that Photoshop made a shortcut for doing it.
Happy flash-stepping!
NOTE: You can also try a reverse of the sequencing above to see a flash-step into the pic (rather than out of the pic)
