AC guinea pig...

I always hold the cans upside down and even lift it above the gauges to get it all emptied. Don’t know why that would be a bad thing. When you purge, it should only take a few seconds before some Freon comes out. Then you crack open the low side and you should be able to see it flowing in through the sight glass in the gauges. With it being that hot outside, I think you should expect around 40-50 on the low side and 150-200ish on the high side. That’s what my system read the other day and it blows nice and cold.