All my horses are always taught to cross tie. It's so much easier to work with them tied that way. I must first say that they are only taught to cross tie when they are very confident in standing tied single and are comfortable with that. I do not cross tie babies at all. You must realize that when you cross tie a horse, you have taken thier "face away" completely and that causes panic. So, you proceed slowly and never, and I mean never leave a cross tied horse alone unattended and even the most broke horse can flip and break their necks.
The way I do it is to have a assistant pretend that "they are the other post" and assume that position. So, the horse is already tied on one side, but the assistant is the other post on the opposite side and stays put and doesn't move; just holds the rope in place as if the horse were cross tied already and that teaches the horse that he is now been "snatched" for better use of another word, from both sides. I let him be comfortable just in that position and I go about and do whatever I need to do while the assistant stands there being the post. Eventually, I will attach the horse to both posts but I do a single free knot where all I have to do is give that rope one jerk to free the horse if she begins to freak and is in danger. But if the horse is just being goofy, I'll calm him/her down and possibly loosen the rope a bit just enough for them to "get a grip" but not untie the horse because that is their ultimate goal, chooseing not to participate, and also not act like I am rewarding the horse for freaking out/ There's a happy medium in there where you need to know when your horse is actually scared and in harm's way and when your horse is just not being patient.
EDITED to add: Hi Bill I just saw your post and read about your soon to be snazzy grooming room and boy that sounds like pure heaven to me. I'd love one of those and would live in it.
However I would loose the heat and air-condition. That's because eventually the horses do have to come back out of there at some point, even sheeted or not and when they do, they are going to have to acclumate all over again to the elements be it heat or cold and you are really risking some health issues doing that. Learned that one in Florida a long time ago from some over-zealous people that kept their horses sick constantly doing that. Actually, one of my barns was screened to the hilt due to mosquitoes and we ended up having to remove the screening because the oxygen level was compromised too. Just a thought for you to ponder.