1. Start by creating a new layer on your artwork. Add the gradients and shadows that you want halftoned.
2. Once you’re satisfied with how it looks, select the new layer with gradients you created. Copy and Paste it into a new document.
3. Go to image > mode to convert to grayscale. It will ask you to flattened the file. It’s OK to do so at this time.
4. Once that step is done, go to image > mode and select bitmap. Once it’s bitmap, select halftone screen, and select the options you want. I usually try to keep it 300dpi and choose round for the bitmap shape.
5. Once you have the halftone screen, turn it back to grayscale (image > grayscale)
6. Duplicate a layer so it’s not locked anymore. Then on the new layer click select > color range, and click on the white area. This will select everything that’s white.
7. Once it’s selected, just hit delete to get rid of the white. Drag the layer with just the black halftone back to your artwork file.
8. Align the layer so it fits where you did the gradient before, then do a color overlay, I usually try and select the same color as the main layer, and then make it slightly darker color.