Step-by-step: Two ways to create a watercolour effect
1 For the Zoe Piel method, use a built-in Photoshop paper texture to Fill the Layer Group mask (highlight mask, Edit>Fill>Pattern/Custom Pattern), or even paste a greyscale scan of real paper into the Alpha channel of the Layer Mask. Then adjust the Levels of the Group Mask. Notice that my Scanned Pencils layer is outside the Watercolour Layer Group. 3 For the post-production method, I take my master art layer, duplicate it and run the Photoshop Watercolour filter. I set the brush to its maximum size and all other settings to zero. Next I select the Reduce Noise Strength to six, Sharpen Details to 100 and all other settings zero. I duplicate that layer and blur it between two and six pixels to simulate pigment bleed. 2 When using the Smudge tool as a Blender, a simple Round soft brush works fine, but Zoe recommends turning on Scattering in Brush Settings, and dropping the Hardness setting to zero. This prevents the creation of a smeary effect and results in more realistic blending of your colours. Spend a little time adjusting the settings to find a combination you like. 4 The filtered layer is then set to Screen at 100 per cent, the Blurred Filtered layer that’s under this is set to Multiply at 100 per cent, with the master art at the bottom at about 50 per cent Opacity. At the very top is my paper texture which is set to Overlay or Soft Light. I sometimes add a second texture set to Multiply. Adjust the layer Opacities to suit.