I don't know about the citric acid mix, the vinegar works just fine by itself. But only put it on weeds, it will kill whatever it touches. Not sure what thread you were asking about.
Once you get your beds weeded, your best protection against having to keep weeding them is a good layer of mulch, a few inches thick. Can be wood chips, leaves, straw, shredded paper, sawdust, grass clippings or whatever you've got. Holds moisture in the soil and suppresses weeds.
But unless you put a really thick dense layer of mulch down, it really doesn't work to put the mulch on top of the weeds and even then, it works better to at least chop/cut the weeds down. In established beds, there's just not much substitute for hand pulling the weeds to start with. Unless stuff is planted in rows, it's hard to hoe. If you are just starting a bed you can till or solarize (lay black plastic down, to heat the soil enough to kill weed seeds), but can't do either in established beds.
Here's an older thread about weeding:
A flower garden and 3 vegetable beds doesn't sound that unmanageable for getting weeded out once to start the season. Just do a little bit at a time! But if you have health conditions or other circumstances that prevent that, maybe you just need to hire/find help with it.