Is there a painting techniqueto disguisea badly patched wall?

Here you go:

https://www.housepaintingtutorials.com/wall-painting-techniques.html

Hi Cheryl, here are a few techniques you can try - https://www.bobvila.com/slideshow/12-easy-fixes-for-a-botched-paint-job-49719.

Hope this source help you https://nimvo.com/a-painting-technique-to-cover-flaws-in-a-bad-wall/

Try using textured paint.

Repaired or patched drywall or walls in older homes have scars you can hide by adding textured paint or a faux Tuscan paint finish. ... Other methods involve adding a secondary glaze coat by color washing, dry brushing, ragging and more.

You can go with a textured paint or technique.

The best way is to fix the patch if you can. If not, you can purchase items to create texture or if it's not awkward, hang some wall decor over it.

Sponge painting covers up flaws

https://www.thespruce.com/diy-sponge-painted-room-1974313

https://www.homedepot.com/c/ah/how-to-sponge-paint/9ba683603be9fa5395fab9019a3613b

https://www.youtube.com/watch?v=n2XaGFLw-xk

https://www.youtube.com/watch?v=obLfSvUIxgE

HIDE YOUR HOME’S WALL FLAWS WITH BEAUTIFUL TEXTURING TECHNIQUES

https://westlakehardware.com/resources/tips-tricks/hide-your-homes-wall-flaws-with-beautiful-texturing-techniques/

You can buy a textured roller, spray Homax texture on the wall. Put painters sand in the paint and add texture.

Here's a post that might help https://www.hunker.com/13411597/painting-techniques-to-hide-flaws-in-drywall

Can you just sand down the badly patched area and re-paint flat rather than trying to cover up the mistake?

Hello. Here’s a link that might be helpful

https://youtu.be/5Cdyqu40nGA

I would sand it down as much as you possible can before painting over it and a primer and extra coat.

You could plaster in swirles to cover it up then let dry and paint