iirc I have mine somewhere 200-400ms delay but it'll depend on what you're playing, mix down at about 1/4, feedback to taste. imho for getting that kind of effect you're trying to avoid very obvious 'delay' effect so keep mix and feedback low initially and listen as you tweak.
If you want to go the software route, download the free Delta fx pack from here http://www.expdigital.co.uk/freeware.htm Included is a delay plug called Delta Ping which you can set to either 16/32 or 32/64 divisions giving a pretty good double tracked sound. Well worth checking out imo, especially as these fx are free.