You may not have rinsed it all off and locked in the shampoo suds under the HGG, or used too much HGG in those areas. Have you tried a clean, dry MF by itself? Ok, maybe a little elbow grease, too.
If the above doesn't work, do you have anything else on the car besides HGG, like PS, wax, etc? If not, Eco APC and a towel will strip it off, then you can just reapply. But if there's anything else besides coating, I'll take it off, too, so you will need to reapply it all.
As for process, when I use HGG, I apply and remove it one panel at a time. If the car starts to dry, just rewet the surface. Since you like to use it indoors, you can use a spray bottle.