I've tried hammering long 6 penny nails by hand. Disaster! Maybe I just suck at it, but I split a lot of 2x4s and bent a lot of nails. And that's straight on, forget toenailing!
Then I bought a palm nailer. Those are great, because one palm nailer handles many different sizes and type of nails. I love my palm nailer for smaller nails, it's awesome for doing siding for example. But those darn 6p nails still bend, even with the palm nailer.
I gave up and went to screws. For long screws I use square or torx drive (Phillips tend to strip when you get into longer lengths). Screws zap right in faster than a hammer, suck parts together tight, and can be backed out if you change your mind. Screws are admittedly slightly weaker in shear, so for shear loads I just add more screws.
If I really wanted to use 6p nails instead of screws, I'd get a real nail gun. If you don't have/want a compressor, I think they make cordless piston nailers with a flammable gas cartridge and spark ignition when you pull the trigger? I've seen them on Hometime.