I tried to do my first diy patch job before painting and it did not turn out well. The first coat of paint was applied and I wanted to know how to fix it. Any guidance is appreciated and please keep in mind I’m a newbie.
You need to sand and then re-coat it will be a bit tougher to sand with the paint on there but it will come off. To do a really good job sand just until you see the paper, wipe down with a wet cloth to remove the dust, then apply another coat of mud, I suggest a 12” wide knife or wider for best results you don’t want a thick coat. When put on two thick it shows more shrinkage so a quick sand and fill again may be needed, I shine a light on the work prior to painting , put the light close to the wall and look to see shadows on the other side of the patch. Lightly sand and recoat a wider patch will be less noticeable when you have a bump to hide, when I was a kid and learning it would take me 3,4,5 coats to get it good enough for my dad, today I usually get it in 2, sometimes 3 coats don’t rush it use light coats, And a light to show imperfections, they will be there the trick to hiding them is wider and uniform patch then a light spray texture can make it really look like a pro job.
Yes, the even, consistent surface is revealing the flaws!
Ignore the paint altogether. Do the patch-up in the normal way. Get it flat, then paint the area with primer and see how it looks.
Tell you the truth, in restorations of wooden historic artifacts, we repeat that cycle as needed. 1) Fill/sand the surface to get it as close as possible "by eye" 2) a coat of appropriate primer to make the surface the same color, 3) look for defects, and if any, go to 1. And we'll repeat that cycle 2-3 times as necessary.
So you just did the first one with topcoat. Oh well! Now, alternate between fairing/leveling and a coat of primer until you're happy with how it looks primed. Then topcoat!