I was just wondering how some artists are able to fade in and out and effect (not talking about track volume). Does anyone have an answer for this mystery?
I am me, in a more literal sense.
Automate the volume of the effect, or the wet/dry control etc. Basically any parameter that affects the severity of the effect in the mix will suffice, though you'll get different results depending on which you automate to fade in/out and how quickly you do so.
Hey, look. Sigs are back.
A few ways to do it, one of the simpler ways is to copy the track and apply the effect to one of them. Then, if you want a fade-in or a fade-out of the effect, you work with volumes of the both tracks, as an example- the track with the effect plays with full volume and at point X of time starts losing volume with a velocity of Y, while the track without effect that plays at no volume at point X of time starts gaining volume with the same velocity.

I use this method on my bands' song I recorded a while ago, here, at 0:10 - 0:14 you can hear the smooth transition.