i wish i could help you, but i haven't ever used efke or ilford's direct positive paper.
i poked around for you, and still came up empty ...
when i make conventional paper negatives i sometimes preflash my paper
to just before it is visible on the paper ... that is like .2 seconds stopped down a little bit ( maybe f8? )
i also use a developer that is partially used, and a water bath, and a developer that is "fresh"
and i go between the 3 baths for a good 2-3 minutes ... i am not sure how the direct positive paper
works if it is a vc paper, or something like " grade 3 " ... but these are tricks i learned just having fun.
i also expose in non-bright/contrast scenes/portraits ( read-- flat light ) so there isn't too much trouble.
the last paper negatives i processed i did so in caffenol c spiked with a little bit of print developer.
the caffenol was old+ used and i used IT in conjunction with the fresh developer and water and it turned out great !
you might try a few different methods with "test strips" so you don't use up all your
paper doing test exposures that didn't work the way you wanted ...
good luck ! i have wanted to try it, but my lack of funds has kept me away from it
seeing it might be addictive + more fun than my wallet wants me to have !