Mudding, Drying, and Not Touching It
Okay, here's the thing. Last lesson we got the mesh tape on and a first layer of mud over your bigger hole. If you did that recently, do not touch it right now. I mean it. Put your phone down and back away from the wall.
This lesson is short on new technique and long on the one skill nobody wants to learn, which is patience. Patience beats skill on drywall. I'll say that a few different ways today because it's the thing that actually matters.
Where you left off
You've got mesh tape over the hole and one coat of joint compound smoothed over it with your putty knife. It probably looks a little rough right now, maybe some ridges, maybe it's not perfectly flat. That's fine. That's what coat two and three are for. What it should NOT look like is wet or shiny anymore. If it's still got any shine to it, it's not ready.
The drying part, which is the actual lesson
Joint compound needs to dry all the way through, not just on the surface. Depending on how thick you put it on and how humid your house is, that's usually somewhere between four hours and overnight. Good news for us up here: our air is dry. Genuinely one of the only times living at elevation works in your favor instead of against you. Compound dries faster here than it would somewhere humid. Still doesn't mean you rush it.
Here's how you know it's ready for the next coat: it goes from wet gray to a flat, chalky white. If any part of it still looks tan or damp or darker than the rest, walk away and check again in an hour.
YouTube will lie to you about the timeline here. Every video makes drywall patching look like a twenty-minute job because they cut out the drying time between coats. Budget this whole project over two or three days, not one afternoon. You'll do a coat, wait, do a coat, wait, sand, and you'll be a lot happier with that plan than trying to power through it in one sitting and getting frustrated.
Coat two and three
Once it's dry, add a second thin coat, feathering the edges out wider than the first coat so it blends into the wall instead of leaving a hard ridge. Let that dry completely too. If you're still seeing texture or a dip where the tape sits, do a third thin coat. Thin coats that you're patient with beat one thick coat every time. Thick coats crack, and they take forever to dry all the way through, and then you're sanding wet mud, which is its own special mess.
Sanding, carefully
Once the final coat is bone dry, take a sanding sponge or fine sandpaper and smooth it down until you can't feel the edge of the patch with your hand. Wear eye protection here. Drywall dust is fine and it gets everywhere, including your eyes if you're looking up at a wall repair, which you will be.
Go light. This is where I have to tell you about my first patch ever, because I did this exact thing. I sanded so aggressively trying to get it perfectly smooth that I sanded right through my own patch and ended up with a bigger hole than I started with. Genuinely worse off than before I touched it. So: light pressure, check with your hand often, stop the second it feels flush. You're not trying to polish it. You're trying to get it flat enough that primer and paint hide the seam.
When to just call it good enough and move on
I want to tell you about the one Saturday I spent trying to match wall texture. Some walls have that orange-peel or knockdown texture sprayed on, and matching it by hand with a brush or a texture-in-a-can is a completely different skill than smoothing a flat patch. I spent an entire Saturday on one wall trying to get it to match the surrounding texture. Didn't happen. I tried three different products, three different techniques, and at the end of the day you could still see exactly where my patch was from across the room.
I hired it out after that. Someone who does texture for a living came and fixed it in about twenty minutes. No shame in it. Knowing when to quit is a skill, not a failure, and texture matching is my personal limit. I still try it every time I have a textured wall to patch, because I'm stubborn, and I still usually end up calling someone. If your wall is smooth (a lot of newer construction and most ceilings in bedrooms are), you're totally fine doing this yourself start to finish. If it's got heavy texture and it's somewhere visible, ask yourself honestly whether this is a project or a phone call.
Priming and painting
Once the patch is smooth and dust-free, it needs a coat of primer before paint, even if you're using paint that says "paint and primer in one." Bare mud drinks paint differently than the rest of your wall and you'll see a flat spot in the sheen forever if you skip it. Prime it, let that dry, then paint to match.
Before next time: if you've got a patch curing right now, don't touch it, don't check on it every twenty minutes, just let the dry air do its job. Bring a "before" photo of your worst wall problem to the next session so we can talk through what it actually needs.