My repair guy patched some holes with drywall mud on walls that had been painted with semi-gloss; we went eggshell. He then painted over the area after the mud was supposedly dry. The area did not match the texture of the rest of the wall and it had tiny bubbles as well as the area looking scratchy from the spreading knife. I could see these huge flat areas amongst the textured so I tried stippling the bumps back in with a kitchen sponge; maybe way too soon after painting. I then tried to roller a coat over the area I did. Now I have dull scratchy areas all over the area, but there is some texture. What I need is a novice way to prep the walls so I can repaint and I will get a textured shiny wall like I thought I was going to get. I would like this method to be a good one, but one that does not require expensive supplies or talents I do not have. Help!
The short answer is to repaint the entire wall. When patching, its almost impossible to get a perfect match of texture and color. If the patch is small you might never notice it, but large patches are usually noticeable to some degree. This might be just because the original paint has cured for a few years (probably yellowed too), or it could be like your case with different textures.
It does however sound like the patch might not have been sanded well enough, so the first step is to sand the patch back down so the surface is smooth and even with the wall. The prime the spot, and repaint. If the original wall was painted with a roller, make sure to use a roller again. A patch that is painted with a brush will usually stand out on a wall that was painted with a roller originally.
I have found than an effective way to get some texture over a patch in drywall is to thin some pre-mix drywall mud with a small amount of water in a paint tray. Then use a long napp paint roller to apply the thinned mud on the wall. You will have to experiment with amount of thinning water to add - I found that it takes only a very small amount. Also you can try rollers with different napps. Lastly to get greatest texture you need to minimize the number of roll overs of a particular area that occur during the mud mixture application.