Dividing irises help

[Fordian]

Need to shift some irises, the tall bearded kind with the ground level rhizome. They're congested and haven't been thinned in 19 years; and this year I got ONE FLOWER, poss due to last summer's drought and the week of below zero in the winter (southern Hants, lots of ppl lost old specimen plants 😞).

So, I've dug them up, but what do I do with rhizomes like this? If I cut them to 4" do I replant immediately or do I need to let the scar harden? If so, how long?

Some of the biggest tangled rhizomes broke, anyway, so the same advice needed for those raw ends.

Many thanks.

do I replant immediately or do I need to let the scar harden? If so, how long?
I can't see the subject mentioned so it probably isn't a problem either way.
This says replant within the fortnight.
This article says, "It’s fairly easy to dig, lift or yank bearded irises out of the ground. There’s not a lot you can do that harms the plant much, even if you lose some of the leaves in the process."

I'm thinking, in July I'm not planting into anything water-logged. The roots are quite meaty. I think I'll leave them a day or two.

Thanks for the articles!

@Fordian
Did you watch Monty on tonight's GW, dividing his iris? (last item on the prog)
I'm not totally convinced by his logic. He said that he, too, had poor flowering this year and he agrees with you that this year's lack of flower was due to last year's excessive heat/warmth. The usual advice is to plant with the rhizome on the surface of the soil to soak up the sun but Monty thinks that there was too much sun last year. Therefore he was replanting the rhizome slightly buried, as protection.
This would make sense if this summer was like last summer but so far it's been cold, overcast and soggy! It would make more sense to do a controlled experiment with some on the surface and some buried and see what happens.

Yes! It was amusing, Monty read my mind! 😂