I have charged my ac and also had it done by a pro. One thing i can say about doing it yourself is its cheaper. However if you get it done by a pro in most cases you get a guarantee. The most important thing is making sure you have enough oil in your compressor to keep it from locking up. Also a pro has the ability to pull the vacum on your system to alow for maximum charge and to be certain their are no leaks. the leak detector you get in a can from parts place is far from foolproof. If your compressor has been removed I would recomend a pro. either that or completly drain your system and start over with the recomended oil and freon , and make sure you get a kit with a gauge because you dont want to overcharge your system either. I have screwed up ever way possible believe me its not always as simple as just charging your system especialy when you have had a componet removed. hope this helped.
But charging your ac wont increase the air coming out of your vent only the temperature

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Im not sure on what models they have this but, I have a 2007 ranger and my ac all but quit i could feel justa little air comin out but the motor was wide open. I thought it was one of those vacume activated openers but after basically taking the dash and fender off the truck I found the problem. Under the glove box there is a flap that opens and closes deepending on what you have the ac set on. If you turn it on reg ac the flap is closed on max ac the flap is open. with the max ac on take a flashlight and look back inside the flap there is a wire mesh filter between the fan motor and and the flap. It was completely stopped up. I used some spray cleaner I think mean green and a extended air blower on a air hose to clean it. it works like a new one.It wasnt getting any air to blow into the vents. I hope this helps someone.