OMS and Zest It are volatile solvents that thin the paint quickly in order to apply flat color for toning / staining or large background areas without brushstrokes.
The oils all have a similar effect with a comparatively slower thinning rate. I generally aim for the famous ketchup consistency. Stand oil gives a luscious feel with the brush and retains a thicker consistency.
I have previously posted my experience with impasto gel to get high rise brushstrokes. The result looks like the paint is straight out of the tube despite being 50% gel.
Delicate value adjustments, rapid drying and a nice mid range ( 'tween oil and solvent ) consistency is the exclusive attribute of Liquin. I depend on Liquin and would be quite lost without it. Particularly for layered painting where wet on dry is the go.
This calculator suggests your pixel goal is 82 megapixels for the size print you want. So 82 divided by 16 (your camera) is about 5 shots, call it six to get an even 3 by 2 coverage. To allow for a 20% overlap I would estimate 4 by 3, or 12 photos
I would print the stitched photo at canvas size, that is 24 x 38 by means of using ten A4 size prints and feather them together manually with tape.
This is quite a bit of effort but worthwhile. This method pulls a huge resolution improvement out of a modest camera and then pulls a huge resolution improvement out of a modest printer.