I have been wondering how to incorporate tremolo into worship. I'll give it a whirl on a bridge or two and check it out. I'm not sure what you mean when you say the "washy" sound though. Do your band mates/congregation notice the tremolo effect and dig it? I'm going to using it tomorrow at rehearsal!Love my EHX Pulsar trem. I use it for a variety of uses. Mostly for ambient/tonal variation - say on a bridge go to whole notes with the trem for a washy feel and then Keep it on through the build turn it off when going back to the big chorus. Or as a background wash tone on more spacey sounds like My Soul Longs For You or More Love, More Power. Think Chris Squire's tone on Starship Trooper.
More recently I've also been adding it to an OD/Wah combination to get another variation on a synthy type bass tone. Again, just for songs like the EDM influenced ones by Planetshakers, Hillsong Y&F and the like.