I love pereskiopsis for grafting, but every time i have used superglue it gets under the scion. Humidity domes sometimes work, but they don't apply enough pressure for the scion to fuse to the stock properly.
What you need to hold down the scion and ensure it doesn't dry out is the cling film method. You take your scion and put it on the stock as usual(with vascular tissue aligned of course). Then you take a square piece of cling film and gently drape it over the top of the scion. Next, grab the scion through the cling film with your thumb and index finger to hold it to the stock(do this with your dominant hand).
Then, while keeping the scion held to the stock, take your free hand and pull the loose cling film down and twist it around the stock until it firmly "hugs" the scion to the stock. Now, simply take a wooden clothespin and clamp it to the stock to hold the cling film in position. You can now adjust the scion slightly if it slid off of the vascular bundles.
Wait a week and done. Just keep it in the shade so it doesn't cook the scion. I dont currently have any pictures as far as i know, but i will dig for a bit and see what i can pull up.
Good Luck!
Edit:
I found I picture of some scions just after grafting!