effect fading

A  couple of options....

First, the proper way if you're doing a lot of this--use the Effects Envelopes  There's a tutorial here, Automate mixes with envelopes in Adobe Audition CC but a quick summary:

First, widen the track so that on the control panel at the left end you see a box with the word "Read" in it.  Click on the little right facing arrow beside it and select "Show Envelopes".  Assuming you have the effect set up in the effects rack, you'll be offered a choice of what effect you want to control and, beyond that, which function you want to control.  For example, on a reverb you'd want the Wet Output.

Set markers on the line in the effects track to control the level to fade in or out as you which and it'll do it for you.  You can set up multiple envelops controlling more than one effect.

Or, if you only have one, the quick cheat I use somethimes:  In Waveform view, select Copy to new to make an identical track.  Put this in your multtrack mix with the effect in the rack set to Full Wet, then just use the normal Volume Envelopes to mix between the two versions of the track as required.