It is fairly easy to register with gum prints as you can see the previous
image. You just need to use a couple of pins in the edges of the final
negs and the paper.
You do not need to register in any of the film stages. I found it easy to
contact print slides onto panchromatic 35mm film to give a low contrast
positive (make sure you give a full exposure at this stage). I modified
an old contact printing frame with a couple of pins to hold a strip of
film and taped the slide by its edges to the glass so there were no
location problems in the dark. This was exposed under an enlarger with a
suitable filters - as used for additive colour printing. Then make
enlargements on a cheap ortho film. I wrote to Agfa and they gave me a
few small packs of 8x10 and A4 film to experiment with! Kodak didn't. You
can use lith film so long as you do not use a lith developer - I used a
dilute universal developer.
Most registration problems are caused by the paper changing size during
multiple processing - it helps if you soak the paper in warm water and
dry it before starting the print.