Welcome to gimp-forum.net
Unfortunately your screenshot does not provide much information, If the brush is now 'wandering' check that brush dynamics is set to 'Dynamics off'
Other than that, if I was colouring-in I would;
Set up a grid to correspond to the cell divisions Image -> Configure Grid
Set snap to grid on View -> Snap to Grid
Use a square brush, if you do not make your own, there is a standard 'block' brush, adjust aspect ratio to make a square.
Use the pencil tool, that will not use anti-aliasing, gives a clean outline.
Paint on transparent overlayer in a 'layer-mode' Multiply works.
Saving as a Gimp .xcf image preserves the grid, layers, settings etc.
You might be doing all or none of that (re-reading you are using snap-to-grid/layers/multiply..), send a screenshot like this that shows some settings.
![[Image: ncAC9gp.jpg]](https://i.imgur.com/ncAC9gp.jpg)
Unfortunately your screenshot does not provide much information, If the brush is now 'wandering' check that brush dynamics is set to 'Dynamics off'
Other than that, if I was colouring-in I would;
Set up a grid to correspond to the cell divisions Image -> Configure Grid
Set snap to grid on View -> Snap to Grid
Use a square brush, if you do not make your own, there is a standard 'block' brush, adjust aspect ratio to make a square.
Use the pencil tool, that will not use anti-aliasing, gives a clean outline.
Paint on transparent overlayer in a 'layer-mode' Multiply works.
Saving as a Gimp .xcf image preserves the grid, layers, settings etc.
You might be doing all or none of that (re-reading you are using snap-to-grid/layers/multiply..), send a screenshot like this that shows some settings.