Hey, TTV is fun and addicting - you got excellent results right away! Your Dualflex has some very nice grunge in the VF
Here's a good flickr group for TTV
Flickr: Through The Viewfinder
I have a Starflex, a Duaflex and a Spartus Six Twenty with turret contraptions for TTV use. Though I also shoot through auxiliary vf's, and SLR, TLR and RF camera viewfinders also. By far the most popular images I have on flickr are TTVs of blank walls and the like - people use these for their own fake TTVs.
(Starflex)
(Duaflex)
(Spartus)