Alright, I followed this tutorial by the book, and it worked to an extent. When I was done, I noticed areas on my object that showed white lines. The same areas which I marked the seam I began with, which I then UV unwrapped. Any idea how to fix this problem?
At a guess I’d say the issue is with the subdivision modifer. There is a checkbox on the modifier to subdivide UVs. What this does is apply the subdivision to the UV map so that the subdivision on the model will not cause stretching of textures. However a side-effect of this is that it can distort the actual UVs from what you see in the UV editor, including where the boundaries are.
You have two solutions (at least that I know of) here, you can either uncheck the box on the modifier, or you can paint/create the texture on a duplicate of the original object with the modifier applied.
Thanks, yes! That made it work. 