Someone's been screwing you around. It is NOT hard to finish drywall once it's up, even for a beginner DIY'er.
Here are some tips:
1. The butt joints:
There is a tool on the market called a "curved trowel" made specifically for doing butt joints:
Take a close look at that trowel and notice how it has a very subtle curvature to it. If you sight along the edge of that trowel, you'll notice it arches up about 1/8 of an inch in the middle. Since you hold that trowel at a comfortable angle to the wall when using it, that curve allows a rank amateur to spread a perfectly smooth and symmetrical "mound" of joint compound over a butt joint about 5/64 to 3/32 inch thick in the middle. That's too shallow a mount to "stick out" from the wall even with wall mounted light fixtures, but it's more than thick enough to bury drywall joint tape under.
(My sister did ALL of the drywall finishing in her basement after a flood using exactly the tools and procedures that I'm suggesting here. She had never even held a trowel before in her life. I was too busy with my business at the time to do it for her or help her do the work, so I just showed her what to do and how, and she did it all herself. And, she has wall mounted light fixtures in her basement, and it looks like her basement was never flooded to begin with.)
#2: The drywall tape:
Most newbies have no end of trouble trying to use paper tape. I own a small apartment block, and I have done more than my share of drywall and plaster repairs, and I've been using fiberglass mesh tape for well over 20 years without any problems at all. Pros poo-poo fiberglass mesh drywall tape because they say it's not as strong as paper tape. I say that if there's enough movement in your walls for the fiberglass mesh tape to tear, then the paper tape will tear too. None of them can point to a situation where using paper tape prevented drywall joint problems, but I've seen hundreds of posts on these DIY forums where newbies were wanting to redo their taped joints because of the mess they made using paper tape.
If you use the self adhesive fiberglass mesh drywall tape, you should have no troubles at all applying it to your drywall joints and then mudding over it with either a 3 inch knife for the contoured joints or with a curved trowel for the butt joints.
3. The most important tool in drywall and plastering:
Always, always, always, when repairing plaster or drywall walls, work with a bright light shining light at a sharp angle to the wall. The sharp angle at which the light hits the wall exagerates the roughness of the wall, but it also gives you a much better idea of where you need to add joint compound and where you need to remove it in order to get the wall smooth. When the wall looks OK under critical lighting, it'll look absolutely perfect under normal lighting.
4. Finally, you should know that there are different kinds of drywall joint compound:
A. "REGULAR" or "TAPING" compound: This is the joint compound with the most glue in it. It sticks best to the drywall, but it also drys the hardest, and is therefore the hardest to sand smooth.
B. "FINISH" or "TOPPING" compound: This is the joint compound with the least glue in it. It doesn't stick to the drywall as tenaciously, but it dries the softest and easiest to sand smooth.
C. "ALL PURPOSE" compound: This is just a compromise between A and B so that drywallers can just carry one pail in their truck rather than two. It doesn't stick as well and it doesn't sand smooth as easily, but it saves a lot of space in the truck.
Normally, you would use Regular joint compound for the first coat you apply over your fiberglass mesh. Then, working with a bright light illuminating the wall at a sharp angle, you'd use a paint scraper to scrape off any ridges or blobs of dried drywall joint compound.
(Drywall joint compound is relatively soft stuff, and you can remove it quickly and easily with a paint scraper. Anyone who tells you to sand down each coat of joint compound hasn't done enough of this work to have taken the time to think of an easier way to do it. It's much easier scraping any lumps and bumps off your dry joint compound with a paint scraper than sanding the whole business down. Save the sanding for the final coat.)
Drywall joint compound shrinks as it dries, so you'd fill in the shrinkage with a second coat, this time using Finish drywall joint compound. And, typically, you'd go over that second coat with a paint scraper and apply a third coat of Finish drywall joint compound. Finally, when that third coat is dry, you simply sand smooth, and it won't be hard to sand what you have to a smooth surface.
Then prime the whole wall and paint.