Well, I wasn't speaking theoretically. This is something I have done many times. It works fine but you have more work to do than normal. To be absolutely candid, a couple of times I have had the process fail and had to do it over again, but I still rode home on the patched tube.
Cleaning the tube exterior is the big Step 1. Water from your water bottle, soaked into part of your t-shirt or a sock (or a small washcloth if you pack one).
After that what you can usually fudge some... can't be fudged. Apply only a thin layer of cement and wait. The cement needs to dry on the tube so its tacky... about a minute to let it set. Apply the patch, and spend more time than normal pressing the hell out of it onto the tube (I use two quarters I keep in my kit. Fender washers would probably work better). Then let it sit uninflated for another couple minutes. Lastly don't try to pump air into the tube to check it before installation. That will distend the tube more than what would happen if its under the tire, and if any slime has leaked in will give it a chance to gain purchase, spread and ruin your patch. Give it just a little air to form a tube shape, get it in the tire, and then reinflate.