HariesDesign.com This tutorials will explain about how make clouds animation, no script needed, it just simple step. Minimum Flash 8. It shown like this:

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Step 1

Create new document with dimention 350px X 350px

Step 2

import your photo collection

File > Import > Import to stage

Step 3

use align tools to make best position

Step 4

create new layer and name it with cloud, and then use brush tools to create cloud in left site ( out of main layer area )

Step 5

still layer selected, press F8 to convert with symbol, select movie clip types

Step 6

Still selected  from Filter panel,select blur types 

Step 7

Still same layer selected

Then from Properties panel, use alpha color

Now you get 

Step 8

Create motion

Insert > Time line > Create Motion Tween

 now move to frame 60 then press F8

Then move your cloud symbol to the right side, like this

Step 9

Test your movie Ctrl+Enter