Game Asset texturing; high poly to low poly

Question

What is the "proper" way to texture detailed game assets? I have baked a normal map and now I want to add color, logos, warning signs/stripes, and all kinds of details to the low poly asset. The details need to be in the correct positions (on insets, recesses), so doing them on the low poly UV map doesn't work since the low poly doesn't have these. How would I go about this?

Do I use the normal map as a UV layout background layer in GIMP and paint on it accordingly?

Do I create a UV map for the high poly as well? (I'm not seeing how this could work, and also the normal map baking worked fine without it too)

Do I add stuff on the high poly mesh and bake them on the low poly mesh like I did with the normal map? How is this done? (I tried something like this, but got an error that I couldn't figure out)

Search results of "game asset workflow", "texturing", "texture map baking", "high poly to low poly" etc usually yield:

• Tutorials of adding a simple repeating texture pattern (brick walls, wooden barrels) onto the object.
• Making just the normal map.
• Texturing an object but very little to none about transferring the stuff onto another object.
• Using GIMP/Photoshop to paint stuff on the UV map of the low poly (Which in my case is missing all the edges of the high poly)
• Something along the lines of Rest-of-the-owl i.e. "And then you just texture it. Thanks for watching."
• Something completely unrelated.

Have I done this completely wrong? Should I have added textures/materials while I was making the high poly? Am I missing something?

Things to note:

• The high poly is one mesh, there are no separate parts.
• I'm an absolute beginner with this stuff
• If there is a way that is better and/or I haven't considered, please do point it out.

Thanks in advance.

EDIT: Not seeing the image description so:

From left to right: High poly, low poly with normal map, plain low poly

Answer 1

In case someone else is struggling with the same issue (Cycles Render):

Presets:

1. Make a UV of the low poly
2. Make a UV of the high poly (Smart UV Project did a wonderful job)
3. Make a new material for both objects.
4. Make a new image in the UV/Image editor for both objects
5. Add an Image Texture in the Node editor for both objects, with their own images (those made in the previous step) assigned to them. If you can't add nodes, tick the Use Nodes box
6. High poly object was painted in the Texture Paint mode, Display mode/Viewport shading set to Texture. Face selection masking was enabled, in order to paint specific faces. Brush set to Fill
7. Hit Image > Save Image once in a while in the UV/Image editor so not to lose hours of work. (It did this to me a few times.)

The baking:

1. Go to Render > Bake, like you would when doing normal maps.

2. Set Bake Type to Diffuse and then uncheck Direct and Indirect, leaving only Color toggled on. (Because if there are no lamps in the scene, the result will be dark)

3. Remember to tick the Selected to Active box.

4. Select both objects, the high poly first, the low poly last. Making the former the Selected and the latter the Active

5. Make sure both objects are occupying the same coordinates / are in the exact same place.

6. Hit Bake and wait.

Like I said in the original post: I'm very new to this, but these steps got me the results I wanted, or at least I can use it.

Here's a pic just for good measure, don't mind the ugly colors, those were just for the proof of concept.

And here it is in Unity almost finished