What do you mean by touch up? Is the bad place in the wall through both layers of paint? If so, you'd need to replace both layers. If not, replace the top layer only. You'd want to use the exact same thing in the exact same sheen, or it might show. If you did it yourself it should be easy. If you had a pro do it, why not call her and ask her to give you a quote on the repair?

It was hard to take pictures of the texture because it is very subtle. Even from a few feet away, it looks like the wall is only very slightly textured drywall. I was able to take these with very bright, direct light. I increased the contrast to make the texture easier to see but I'll post the original picture, too. I think they used a roller and then blended out the edges with a brush?? I was able to blend the touch ups that are near the light brush strokes with a small paintbrush. But my other touchups stand out because they are too smooth. I think I need to use a different type of roller? I also noticed this when I was taking the pictures. It's a windowsill, and it's the only place I've found that looks like this, and I don't know if it's the paint or drywall. With the exception of art painting, where I am conscious of my brushstrokes in a different way, I've never painted anything in my house with the intention of leaving a texture before - it's like the opposite of everything I've practiced. I have painted a lot of furniture and cabinetry, and I practiced so much to learn to lay thick adhesion primers without strokes! And back then I couldn't find any tutorials about proper technique, I just sort of experimented until I figured out how to do it. So, I'm not exactly sure how to manipulate it, and if there's a proper technique I should learn.

if you are selling match the yellowed trim

The same thing happened to my custom kitchen cabinets. The trash pull was the worst, chipped all over. I had my contractor come back and look at it (2 years later) and he sent his (new) painters in who verified the wrong paint was used. So at his expense he took all the doors and sanded and repainted them (professionally resprayed) with the correct paint. It’s been 6 months and not a scratch to be found, and we’re pretty hard on them. My thoughts are that painting them with a brush is never going to look right, even if you somehow found the exact same paint which is next to impossible because paints and painted surfaces change over time and with use. Painted cabinets by nature are prone to chipping but if they’re done correctly (according to my contractor) it should be minimal.