Although your spray painting service trademark may be registered and not in the same category as other people's paints, you still want to imitate other people's famous brands. If you use it on products in this way, it constitutes infringement and will cause consumers to misunderstand that you are related to XXX Paint. 1’s approach will obviously constitute infringement. Unless your registered trademark is not similar to other people’s paint trademarks.

Method 2 will still cause infringement if you actually use a trademark that is similar to someone else’s trademark on the paint or mistakenly think it is associated with someone else’s paint trademark.

If your service mark is different but not similar to someone else’s paint product mark, you can use it in any way. The approach you envision may deceive some people for a while, but in the end the gains outweigh the losses. If you don't have the time to think about others, why not create your own brand? After all, it is your own "child". A gentleman who loves money should acquire it in a wise way.