elainew, Congratulation on your 1st. castings! lots of fun isn't it!
I usually try to peel my leaves of within 24-48 hours of casting-that is if the cement leaf bottom pass my "no-scratch" test first. Some leaves are very stubbing but give them time before getting to rough or you could loose some of your leaf detail. As far as covering I keep mine misted using a plastic spray bottle then cover tightly with any kitchen plastic wrap, then a heavier plastic cover. Keep hydrated for at least 7 days. If the weather is hot enough too create it's own mist I put recently created cement items in a plastic bag in the hot sun, put a wet rag inside if you can't keep a check for moisture. I don't paint till after this curing process or longer and I have so much to paint right now I'll be busy all fall, maybe even longer!
If the stem holes are on a small leaf (like 5"-7") I thread heavy twine or a ribbon as such for a wall hanging, once painted these make wonderful little gifts; or, I'll fill in the stem hole (EE leaves are famous with this) with a thick slurry of wood glue/water/dry cement,(no sand) this may take a little time to set up also. The bug holes don't bother me - although I do use a very diluted wash of black craft paint and water to disguise the little buggers! LOL
Hope my experiences can be of help. I acquired most of my knowledge here also. Wendy

Thanks Wendy. There are so many little tricks that make them better from what I've been reading. Most of the leaves are out but I still have a little picking to do. When I pulled the plastic up around the leaf/cement some of the cement rolled over top side of the leaf making the edges messy. I guess I need to be more careful.
I also used a little hunk of granite to smooth some of the bumpier edges. I learned that technique is sensitive too as I knocked off a few chunks I shouldn't have.
I'm thinking that this is like my first pancake. Always just a bit off but then you get the hang of it.
I used Quickcrete straight from the bag. Maybe next time I'll try the Portland recipe to make it smoother.
The more tips the better. Can't wait to paint them.