Here is a starting point for a shoegaze reverse reverb sound.  For reference, listen to "While You Sleep" by My Bloody Valentine.  In general, you want to use reverse reverb before fuzz and/or overdriven amp while playing with the tremolo arm.  The reverse should be fairly short - it smears out the attack and gives it a textural envelope.

We tried to keep it as simple as possible, with just a Context 2 and a fuzz into a clean amp.  We used a smallsound/bigsound team awesome! fuzz machine (TAFM), because it has a slightly gritty clean blend.  The signal chain is:

guitar --> Context 2 --> TAFM --> amp

The Context 2 is set to reverse reverb with the blend at 2:00 to let some clean signal through,  some predelay (11:15) and a short decay (10:30).  High response is at 3:00 and low at about 1:30.  We like to set the mod control around 3:00-5:00 to add some forward reverb, for a wall of reverb out of the Context.

We added a little delay as well, with delay time at about 11:15 and feedback around 11:00.  Delay/reverb balance (bal) is  at 11:00, so there is just a hint of delay but you hear the repeats when the notes trail off.

The TAFM's clean blend lets some of the clean reverb sound through with the fuzz tone.  That helps it keep its shape and makes the sound more complex.  You could also use stereo output from the Context with one channel going through a fuzz and the other clean, into a mixer or two amps.

Finally, hold the tremolo arm with your pick hand so that the notes bend as you play them.  You can also experiment with different tunings. 

Here are the settings, with a screen shot of the Context web editor to show the delay settings: