If you are getting a funky flat looking positive, you are half way there.
The interpositive should have good shadow and highlight detail for later
reproduction.
I suggest developinging the interpositive in D23 1:3. I find my time for
development fall between three and six minutes. Just for the record, I use
4X5 or 8X10 FP4 and make the interpositive by contact printing. And then
projetion print the copy negative tothe size i'm looking for. The copy neg
is developed in Dektol 1:6 again, between 3 and six minutes depending on
the image and what kind of contrast needed.
You could also use a direct positive development technique that eliminate
the need to make two generations. This uses a dichromate bleach,
re-exposure to white light a sodium sulfite clearing bath. There is couple
of commercial chemistries for this on the market. I use an inexpensive kit
sold by a small photo-chemical house here in Tucson called Coldlight. I
don't have their address or phone number handy. It is about seven steps in
all. My students prefer this to making interpositives because they get it
done with one sheet of litho. If interested I'll dig up the info for you.
Also, Tillman Crane has a nice paper on making direct positives on his
school homepage (www.waterford.edu)
I stopped using direct positive film because of the cost and the fact that
kodak only makes the stuff in 4X5 and 8X10 sizes.
Hope this helps.
Joe Portale