Sock tutorial:
Search for pictures with feet and without socks.
Example
https://booru.allthefallen.moe/posts?tags=feet+-socks&z=5
Choose a picture where the lower leg can be selected easily and it's not obstructed
Example
https://booru.allthefallen.moe/posts/927626?q=feet+-socks
Open the image in gimp
Separate the lower leg into layers
Duplicate Layer
Add alpha channel
Use:
-Free selection
-Diffuse selection, antialiasing, feather edges, threshold 30, radius 1
to remove the unneeded parts of the image (images 1-6)
-Move the selection so one border matches the new sock border, and put the pivot there, then rotate so the line goes along the mark (image 10)
-Repeat until the new border is complete (image 11)
-Rotations may smooth the border, darken it as needed with the paint brush (images 12 and 13)
-Copy and paste to fill the sock gaps as needed (image 14)
-Smooth as needed, but keep the texture
-Remove shadows as needed using copy and paste again (image 15)
-Select the bottom curve of her shin to use as the new top of the sock. (image 16)
-Remove the top of the leg, which should not be covered by sock (image 17)
-Paste the sock top in a new layer. Move it so the tip of the border matches the top of the leg (image 18)
-Put pivot in connection point and rotate into position (image 19, 20)
-Make the layer semitransparent, notice that you cut too much leg (image 21)
-Copy from image 16 the required part of the top of the leg into the sock layer (image 22)
-Remove unneeded sock top (image 23, 24)
-Smooth and clean the sock top (image 25)
-Check with original image as background (image 26)
-New from visible with sock and sock top layers to obtain a new layer with the whole sock
-Colorize to select the desired colour (image 27)
-Repeat for the other foot
Remember to post your results!
-Color -> Desaturate -> Color to Grey (image 7 is now our sock)
-Smudge, select, copy and paste as needed to remove unneeded deatail like fingernail or inter-finger separation. (image 8)
-Create a new transparent layer, and call it notes. Use the pencil tool to mark lines with the convex hull of the sock. (image 9)
-Copy and paste the border of the image, and rotate as needed to reconstruct the sock border, use the notes layer for guidance.