Using the Boolean AND paste function to apply a ramp-off to a sequence will only work reliably if the the section of the sequence to be faded has cells at either 100% intensity or 0%. Applying the Boolean AND method to fade cells with intermediate intensities will give unwanted results.
The technique given below uses the shortcut key combination Ctrl-Dn (hold down the control key and press the down arrow key). It is a roundabout method but I do not know of any current one-click method of doing this.
The default for Ctrl-Dn I think is to decrease all selected cells by 10%. This value can be set from Tools – Preferences – Sequence editing. Enter a new value in “Intensity adjust large change (% points)".
Select the cells of the sequence that you want to start fading out. Then use the Ctrl-Dn key combination to drop the intensity level.
Then move a few cells to the Right, reselecting the remainder of the sequence to be faded. Once again use Ctrl-Dn to decrease intensity.
Keep repeating this process. Eventually you will get to the point where the sequence has entirely faded to 0% and you can stop.
Depending on the type of sequence you wish to fade it may make the section shorter than you want so you will need to select more cells to the right of your desired end point to compensate for this.