How to fix overlapping parts on texture?

[CLE_AA-5B_GrummanTiger]

I'm still relatively new to the livery game, but have successfully made a few. I'm running into a new problem now that I'm not quite sure how to solve: namely overlapping aircraft parts on a texture. In other words, when I want to paint a specific part on a plane (in this case, the Bonanza's stick-out notch on the leading edge of the wing), it also paints a part underneath by the wheel well. The UV file confirms that, for whatever reason, those parts do overlap. Obviously, this is frustrating.

One solution someone posed is to simply slap a decal on the part (I suppose either, depending on my preference). Problem is I don't know how to create decals and how to "slap" one on. Is this about the only way to go about it or is there another method I'm unaware of?

And if the decal method *is* the best method, can someone kindly point me to a tutorial on how to go about it? I've already searched for videos on this and there's only a few thousand of them to wade through and I'm hoping some of you know a good one somewhere in the middle of all the search results.

Thanks in advance!