I understand that Houdini is not a texture painting app and there are better DCCs for this job such as 3DCoat and Substance Painter. But giving what Houdini has now, from the new COP to Texture Mask Paint SOP, I feel it should be technically possible at least for low-poly models. After all, 3 Texture Mask Paint SOP can more or less paint a texture already... it's just extremely inconvenient as you need to paint R/G/B separately.

I wonder whether there is some makeshift solution (a third party plugin, perhaps?) for a texture painting workflow in Houdini?

The new COP introduction videos have some semi-procedural texturing workflow, like making two procedural textures and blending them by a hand-painted mask. But how to hand paint a colored texture instead of a mask directly? Attribute Paint SOP kinda does that, but it doesn't work in texture space, but on point attribute.

raincole
But how to hand paint a colored texture instead of a mask directly? Attribute Paint SOP kinda does that, but it doesn't work in texture space, but on point attribute.

Project the texels as grid points on the mesh surface, colorize them using attribute paint, and rasterize them inside COPs.