Actually, you can't disable sharpening in-camera when shooting JPEG. Regardless of the sharpening setting in the camera, even if one option is labeled "off" or "none", there is some minimal sharpening done when the initial RAW image is converted to a JPEG in-camera. The in-camera control is merely a choice of sharpening levels.
This means and if you do additional sharpening in post you will be, in effect, sharpening multiple times. That a doublely bad thing since you are not only sharpening multiple times but you are also sharpening the artifacts that resluted from the lossy JPEG compression that were generated when the camera created the JPEG it saved.
If you shoot JPEG you should adjust the sharpening setting so that you get the proper sharpening for each image. This may mean different camrea setting for different images.