I made this video tutorial as an experiment to test whether it is
possible to make a useful tutorial with no microphone and only
a low-end machine without a video editor.
The video assumes some knowledge of the alpha channel.
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Instructions to paint with mtpaint program.
There is no need to use layers feature or a mask.
Additional benefit : the greys in a black and white drawing are preserved.
This protects the quality of the final result.
Start with a simple 24bit RGB drawing in black and white
(see my snowman drawing).
Be sure to use the default color palette.
Note: If your drawing is a GIF document you must convert it to 24 bit color
because pasting an indexed image into a 24 bit image causes the
color palette to become confused.

Select all the document and copy to clipboard.
Save the clipboard to disk.
The original image is still in mtpaint document window.
Use the paint brush or fill bucket to color the document.
Don't be afraid to use gradients or change opaque levels.
You can paint over black lines (see below).

Once the coloring is done, the last step is to fix the
black lines.
Edit > Load Clipboard
(If the clipboard and document size are the same,
then there will be no need to move the selection)
Set the A and B colors to white.
Selection > Alpha Blend A,B
(the clipboard paste now becomes transparent)
Press <ENTER> then ESCAPE keys to set the selection.
Save the finished image to disk.

Note that no layering or masking was used.
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Next a more advanced example which uses a mask.
Make a clipboard file as in previous example.
Mask a region where you want a gradient.
Pour paint with paintbucket (low tolerance to paint over black).

Disable the mask.
Then load and paste clipboard like in previous example.
(Make sure that A/B colors are white to make white the transparent color)
There should be no need to move the loaded (pasted) selection
in the document window if document size hasn't changed.
Delete the mask ...
Channels > Delete
Proceed to mask another region if you wish.
(Gradient will need to be reset to new region of image as well)
This way you can color your entire image in different colors.
Note that the layers feature in mtpaint hasn't been used.
This technique is called 'alpha blending'.
Greys are pasted as well as black. This preserves quality.
Remember the way it is used. Both the A and B colors are set to the
color that you want to be the transparent color in your paste
(white in this example).

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