Size down?
Not for dry denim, for me that would be impossible in Nudies or Denimbirds. I size up one to two sizes for their dry, and even then they're a nightmare to get on the first time; then after a couple of wears or a sleep in them they're more comfortable.
Their pre-treated denim I'd definitely take my regular or a size down for, those seem very large for size. I'm not sure how they end up so big though, given that if we wear our dry denim for a few months and then wash them, they often shrink a touch in the wash! I guess the pre-treatments are akin to wearing them a few years, maybe.
I find that the D'birds dry denim is just the same as the Nudies dry denim, though the sizes seem a little more generous. I have a pair of D'birds Dry Black bootcut that I converted to an almost straightleg in 25/34 that are much looser around the waist and thighs than any of my Nudies; then this new pair I mentioned above of Tight 25/32 in Dry Black, which aren't as large sized as the Bootcuts but are still larger in cut than the Slim Kims despite all given measurements of rise, knee and hem measurements indicating that they should be the same thing.
I also find that the D'birds are longer in the leg - any 32" in Nudies hit at my ankle, whereas the Tights in a 32" leg reach the floor on me. I have a 33" inseam, hence I try to buy the 34" jeans.
As for sizing of other dry denim brands, I've not had much experience, though so far I've worked out that..:
Nudie dry denim - size up at least one
Nudie dry comfort - take your usual size
D'birds dry denim - take same or up one
Edun dry denim - take your usual size
Levi's dry denim - take your usual size
Tsubi dry denim - take your usual size (just jiggle around first time!)
Again, these are from my own experience.
