Depending on the kind of paint you have this method may vary, It works well for me having a soft enamel paint.
You can wash with car wash solution, and a clean microfiber towel.
Make sure to use a different towel for each step, but reuse the same series of towels every time you wash your bike. First fill up a bucket of hot water. Then put a little car wash solution in it. Wash the bike with a micro fiber towel. Then get a clean bucket of water. Wipe it down, and get all the soap off. Then dry it with another microfiber rag. Now you can use a polish
I like to use Bontrager bike polish, because it wont mess up matt finishes on your bikes paint. then spray your polish on, put some on you towel too, and buff out your paint until it is very shiny, and smooth (not wet with polish). Finally take a spray on wax (
I use mothers spray on car wax.) To protect the paint from dirt, and grime when you ride. Take the spray and get your paint wet with it, then with a different microfiber towel spread the wax evenly, let it sit a minute, and buff out. After all these steps you bike paint should look like new, and it will be protected with the wax.
(I also repeat these steps on my fork to protect it's paint as well). This is a good method because you never spray water on your bike, meaning no water will get anywhere other than the surface of the frame. Now, I would use wd-40 for scuffs that you need to get out, but I wouldn't leave any on the paint because it may lift decals up from your paint. All of this is personal preference, but for me it works out perfect for me, so I though I would share it with you.
Happy riding!

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Why walk? when you can ride!