Contrast is greatest near light source and near the viewer

Simply by selecting color range and going to hsb it is possible to affect some ranges more that others. Loading channels or composite can accomplish the same thing. By loading rgb you will shift lighter, by loading r lighter and redder and so on.

By inverting bw pic two paths become open - paint with light and ignoring knowledge attributes. ie shapes become more visible.

Certain blending modes may work in combination with others quite well. Foe example - lighten or darken may knock out large set of values, so next blending mode will affect what remains.

Start with BB. Mix values with color (color burn or linear burn mode), glass pain the result. Use lines to to define outlines if necessary.

Pen can indicate outlines but blue pencil should indicate LIGHT areas, and when imported and separated it should be inverted

Upper leg equal to lower leg plus foot, each of them equal to 2 heads. Base of rib cage twice as wide as its top, rib cage has 1 to 1.5 width to deapth ratio. Base of ches masseles located between clavicules and navel

Interaction may happen in two steps - the way original material interacts is extracted and then reaaplied to the material - the hope is that we will use only parts that interact and those interactive parts will find home in the texture that they interacted with.

cheek bones located at the mid nose level. width betwee cheek bones is width betwee base of the nose and chin. Corner of the jaw is 1/3 from bottom of the chin. eye at 1/2, nose at a bit less than 1/2 of remaining, mid mouth is at a bit more than 1/3 remaining. Nose base at upper eye lid. arm spred is the body height.

To avoid wide spread take common derivatives and work with them. For example: SD and Value. SD can be used to subdivide textures, values, colors and gradients. Value can be used to create colors through gradient maps, can be used to create stepping value subdivision with refined network of SD. SD can be used as selection matrix. Interplay of children would create fields of walk. Then talk with rendering.

Burn and Dodge tools approximate lights on shiny surfaces like glass and approach tinted glass. They also increase saturation. Vivid light is a combination of dodge and burn.

Fill brightness and color should take its values from natural media, since only there variations are unlimited. Border pixels can be altered with randomness of hand strokes in those types of brush that produce fragmented patterns like sprays, uneven smudges, fractalized blurrs, splatters, etc.

Self-document progress with layer naming - discover patterns.

Matrix concept is quite strong since it allows unlimited masking and precise adjustment layers.

History brush can be use in conjunction with snapshot and undo. Extra layer may prevent it from working.

Only walks that bind and unite matter.
When image is seen be it in wake or pic, its SD lines, feature lines, values, colors and textures, thir whole orchestration will exist as your part, more or less remote, as forgotten home as forgotten grief. Talk with it, walk with it.
BBB stands for initial Blue sketch, for Black SD and feature lines mapping and Blue values. Original sketch with its general approach should become primary walk for a long time, may be forewer, for without it, other steps are difficult. Axis, angles, blocking, simplified grids, blind eye draw, 3d understanding - all these can be walked. Books can provide backbone of those walks. Both acceptance of word of authors and intuitive experimentation shell be used. Experimentation should be structured in time, results compared for vector of future walks.
In general line-value approach is the most inclusive and it can take form of pure value or pure line sketching, where other component is done on pc. From this point the question is of labs and rendering.