There is a way to paint directly onto your model by texture painting, there is no way that I know of however to directly link the two programs like that…
TGA is higher bit depth than PNG. If you have both programs open at the same time, it is not too hard to save in PS and then just choose reload in the UV image editor - as long as you aren’t going about saving iterations. Personally, I would block out as much as possible in Blender’s Texture Paint tools first, then there is less to work out in PS. Painting directly in the 3d space is getting to be very comfortable, especially if you are using a pen tablet.
But I am not talking about using PSD file as texture image, I am talking about painting in Texture Paint mode in Blender on TGA or PNG, and then taking it into PSD to expand on the painting there.
About doing the reload - yes, PSD is not supported, but if you are using Tiff or TGA, then you will still have high bit depth compared to PNG. Also, you can use Open EXR if you download the PSD plugin.