Your stones are nothing like the ones in the site you linked to; you cannot expect similar results. The stones on edge will disappear and the rounded ones will show too little surface. Further, that remuddled fireplace you linked to looks like garbage--like a bad stone job that used too few stones and waaaay too much mortar. That's the kind of thing that people post in here sobbing about how badly the fireplace (or backsplash or tub surround or...) turned out. Nobody--nobody--lays stone like that with that much mortar, except a DIY homeowner with no clue.

I would sure like to know what is under all that paint and stuff. Could be some nice brick? If not then my thought is something right to the ceiling but no mantel.

yes, prime it first. Clean it first with a stiff brush and vacuum. It will clean off any dust. They try a brick cleaner mixed with water. go over that w/a heavy duty rag or another brush. w/the brick dampened (let it dry a bit if you soak it) it won't absorb as much primer as when dry. roll it on and use a cheap brush to dab the joints. Use something like Zinsser oil base primer or Kilz. If you don't use the oil base, you'll get bleed through: You could also use any paint meant for brick or masonry. (after the primer) it's going to suck up a lot (even more if you only did paint). get a cheap brush to help cover the joints. I like how they did this one w/the decor and shelves around it: I love this matte black one w/a red oak heavy beam mantle. So pretty. photoshopped it onto your pic. lets see the entire room. if you have white walls, this would look nice The addition to a nice rustic wood beam mantle can be done w/lag bolts. or, if you prefer the white, add the wood beam and think about doing black stone on the hearth. Basalt tile (or a granite or soapstone) is simple/inexpensive addition. easy to DIY Photoshopped this one w/the white stone hearth and dark stained Fir beam mantle. also easy to DIY. you could use a remnant leftover of quartz or some type of white marble if you like. If you do the primer and then paint, use the eggshell or satin finish. Romabio has a masonry lime 'paint'. you may not have to prime if using that one. you can have it tinted any color. (don't confuse it w/the romabio classico which is a limewash) Other options: you could also do a cement or stucco overlay (smoothed out) if you want this look lay on a coat of primer first or else the brick will suck out all of the moisture from the coating https://angelarosehome.com/diy-a-cement-look-fireplace/ diff ways to do it. the one above is a cement overlay w/a smooth coat. this one is more rustic. could be a plaster coat w/a wood trim panel done above I also like the black If black is too harsh, try something like BMWrought Iron, or Iron Mountain is the color for this one: I think the black w/the wood is stunning. adding in some nice built-ins B/A w/cement overlay application: another B & A. If you want to read the how to on this one, here it is. I don't think she used a primer and only used Behr paint https://www.hugheshomediy.com/post/how-to-paint-a-brick-fireplace If you choose the dark color, I'd still do a primer. Have the primer tinted to a very dark charcoal or black. (primer can be tinted any color). This way, the brick won't absorb a ton of paint, and w/the primer tinted in the dark color, you won't have to do as many coats

BeverlyFLADeziner, I did. lots and lots of videos… yes i have to admit i got cold feet early on and tried to get a bunch of the mortar off ( if u can believe there was actually more) the mortar is too white and kind of looks more like German smear than overgrout. the video tutorial i watched used white mortar but i think their tile format was bigger so i ended up with more mortar than brick 🤦‍♀️