I've got a detachable run and want to move it to fresh grass from time to time so feed is sort of an afterthought. Definitely will have water. I just want to encourage them to forage grass. Is there a time limit for them to be without feed?
For starters, I would let them eat from the feeder first thing in the morning. You could put them out for a while, then allow them back to the coop at night. Watch your production of eggs to see if they are getting enough feed with what they forage.
Mine forage all day long, but seem to go back to the coop at some point to eat. I don't know the mechanics of this, because they have 3/4 acre for the ten chickens to forage. As spring progresses, new plants grow that aren't around in winter, and there are more bugs, worms, and other things to eat, they may be eating less feed. At least it seems that way.
Feed consumption seems to be down about 15% versus winter.
Nevertheless, they can eat their feed at any time.
They will need water in the movable run.
As with many things, you may just have to experiment with all this.
A common practice for me is to use scratch mix when the birds are confined to a run. Sprinkle it around the grass in the run and they will scoop it up with no problem while foraging. You don't have to be overly generous with scratch as the grass and bugs, etc. will keep them pretty happy.
It would be a good idea not to put feed into the run unless they are cut off from the feed while in the run. Chickens are spoiled creatures and it is good to have food accessible to them at all times. As you indicated their feed habits will drop as the grass and other goodies are available and it saves on the feed a bit... Water in the run, definitely, scratch is optional but access to the feed necessary in my books.
Being from Eastern Canada the names of the feeds differ and recipes in the feeds differ as I mentioned (scratch), Others that post may have different but useful advice as well. I just stick with what is best for my situation and it works. My birds are all free range and I use scratch religiously as a foraging treat in a couple of small areas. Steve