Rectal is pretty easy and is way more similar to shooting it than smoking/snorting. However, if you're constipated, then it won't be good to administer it rectally. You need to be cleaned out pretty good. You could always use an enema before if you're that desperate. But this is a huge hassle. Maybe not so much for you at this point since it's all pretty much a hassle by now.
With smoking on foil, it just takes some practice. I got pretty good at it. There were times where I would be so sick that I would take a couple hits before shooting just to calm myself a bit first. You make a little canal in the middle of the foil and then just ever so slightly tilt it while holding a flame underneath. You also can keep the flame pretty far away from the bottom as you only really need to get it just hot enough. A small stream of smoke is what you want since if you get it too hot, there will be more smoke and it will lead to waste.