My approach is not as scholarly as most. Sometimes while practising/doodling, I will like the doodle enough that I will want to see it realized into a full painting. The Sirens image was originally three individual sketches from my figure drawing practice sessions. I had originally been trying to go for an art nouveau style, which at the end, you will see is completely lost.
After the basic framework is laid down, I excitedly moved on to the painting phase. In hindsight, if I had spent more time in the sketching stage, it would have most likely produced a much better final image, and might have even maintained its original art nouveau style, but NO! So HARK! I think my next piece will reclaim that endeavour!
Initial Stage & Methods
I created a new layer filled with mid tone gray set to multiply mode and merged it down. The gray tone becomes the predominant background colour. This is important since if you were to have a stark white or black in the background, since they are extreme in contrast, its difficult to discern tonal value. Throughout the painting stages, my normal process includes copying the main layer, and leaving the original for backup. The short-cut Ctrl-A, Ctrl-C, Ctrl-V (select all, copy, paste then followed by Ctrl-S for save) is something I do all the time. I work on the copied layer in small stages/sections, and once satisfied with the appearance, I will merge down (Ctrl-E) to the original backup layer. Many online viewers have told me that my style has a very 'smooth' airbrush appearance. I think the result is from the many times I merge the duplicated layer to the main layer with varying degrees of opacity. Over several iterations of merging varying opacity layers, the combination results in a wider gamut of tone. While painting the working layer, I will sometimes over paint, or paint too dark or light, where ever it is needed, then reduce the opacity of the layer to compensate (Quite a bit sometimes, even down to 7-15% opacity). This is very helpful for sections that have a very subtle shadow/highlight. This is similar to glazing oil painting techniques where the painter builds up form with multiple layers of thin glazes. Let's get to colouring!
Using a flesh tone, I used a multiply brush at 100% to lay down a base. Seeing that it wasn't dark enough, I cover the area with the same brush at 70% opacity. I'll go back and erase the over paint later. Using a blank layer, I use the same flesh tone swatch with normal brush at 40% and buildup the lighter areas. This stage is a little discouraging because you will start to lose the line art and it will look like bullocks, but forge onward brave ones!
Using the dark swatch shown (2.), I reclaim some of the lost line art details by adding the shadows using a multiply brush at 10-30%. Cleanup and further modeling of the form is done with the original light flesh tone at a low opacity. Now comes the fun part. Using the red swatch shown using overlay brush mode at 7-20%, I've started to accentuate the flesh tones with subtle colour. Experiment with this part. Try using dark purples, blues, pinks, and dark oranges, but make sure to keep the opacity low as the overlay mode is quite aggressive. The example is what the layer looks like before I reduce the opacity and repeat the process until I end up with a satisfactory tone. I also popped in some preliminary highlights on the nose and shoulder with the dodge tool at 20%. After finishing one girl, I moved on to the others. After I had finished all three girls, I used the Hue/Saturation Adjustments to tweak the skin tones to the desired appearance.
Basic Background Layout
For the background, I experimented with Painter. It's very handy for quick painterly looking mock ups since the brushes blend so beautifully. Using a basic blender brush, I threw down some experimental background elements and painted over the excess paint from the skin colouring process. I also started to block in the hair colour.
Definition and design elements
(I will be using the Sarsa hair brushes and splatter brush, found on internet long ago, I do not know the author)