Hi
I have a T1 and love it but use it with Traktor.
Post fader effects can only be used if you are using the mixer to control midi within the software for the mixer section. ie so its like a controller not a stand alone mixer.
The reason for this is that post and pre fader effects are all entirely software based. You basically turn your T1 into a midi controller with built in soundcard and do not use the T1s standalone mixer functionality.
Hope this makes sense
It is not possible with traktor but I have never used Serato so can't answer but I would imagine not.