Anytime I shave my full body which is usually once a month, I always carve out at least five hours of time in total because that's about how long it takes for me to do everything, but then again, I'm a lanklet with dark, curly hair so everything I have to do is even MORE of a pain in the ass than it probably is for most other people here. If you're using an electric razor, which I highly recommend you do at least for your legs since a regular razor will be a ROYAL pain in the ass there otherwise, make damn sure it's fully charged the night before if it's charged via cord so it doesn't die on you midway through the process and anytime you're not using it at all while you're doing other stuff, plug it in to make it last as long as possible. Personally, I've found that I can't use it on my elbows, shoulders or knees because I get bad razor burn when I do that so I'd just shave those with a regular razor if I were you. Strongly advise you to not use it on your armpits, inner thighs, pubes, ass crack/taint or other sensitive areas. Anything you shave, be sure to moisten it beforehand and use plenty of shaving cream over top. I'm lucky to be flexible enough to do just about every part of my body on my own without help so unfortunately, unless you're a bendy boi like me, you'll probably have to have someone else do your back for you (BF if you have one, professional waxer, etc.). Don't be a cheapass and use dull or bad razors because it's really not worth it and you'll probably cut yourself at least once; just throw it out and use a new one.
It's up to you whether or not you want to use a depilatory as well. The pro is that it makes it easier to shave in the sense that the hair you use it on will be weakened and come off much easier than normal, but the cons are that you'll have to wash/change the regular razor blades you use more often because even after you wash it off, the depilatory will probably leave behind a thin yet annoying coating on your skin that will clog up the blades and wear them down pretty fast; it'll probably smell very chemical-ly for a while; and it can be a pain in the ass because you have to be careful with it, especially cleaning it up. I've found that it doesn't work on my face so I wouldn't waste it on that and I wouldn't put it on your junk either since it tends to hurt my balls when it ends up there. Here's a pretty good guide on how to use Magic Shaving Powder, which is what I use anytime I throw a depilatory into the mix: https://docs.google.com/document/d/1YNGUSH6zutTcv_osPURNvH8K19mXiX730Y-JeDRMNbI/edit?pref=2&pli=1.
Don't beat yourself up if the results aren't what you'd like or you get discouraged, anon; I've only been doing this since late last summer and I still fuck things up here and there. It's a lot of work so it may seem intimidating but once you get the hang of it, it'll get easier and everything will practically become muscle memory. Hope all goes well. :)