Very easy. Select LPF and slowly drag your finger down the X/Y pad. Then with your finger on the pad still, select Freeze under section 3. This will lock the low pass filter in place.

Then select REVERB and perform the same action on the X/Y for the desired effect and once again Freeze section 4 to lock in the reverb.
Find the place on the X/Y pad where you froze the LPF and hold your finger there, then unfreeze section 3. Gradually fade back in the higher frequencies by dragging your finger up the pad.

Getting the reverb to fade out will take a bit of playing around depending on when you want that effect to start. You might even be able to unfreeze section 4 while fading out the LPF (thus controlling both effects at the same time) or once the LPF has been disengaged then just fade out the effects depth knob or fade out using the pad just like you faded in.

Keep in mind you still have two additional effect sections left so you can throw some distortion in there and make a stutter with the looper at the same time. Way more fun than learning the presets on the KP3.

The simplicity and immediacy of the Quad sold me over the KP3. I really do wish it had a metal case like the KP3 but oh well, once you start using it and stop looking at it you forget very quickly what it is made of and I have unintentionally hammered on those selection pads with no adverse results.