I've successfully made very tiny decals
This is what I do.
I use this paper:
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I print from my inkjet printer (not laser) onto the decal paper with the setting of quality high, and type of paper high quality gloss photo paper.
I let that dry for 20 minutes or so.
Then I use this:
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I spray five or so light coats over the whole paper, letting it dry each time.
I then cut it out, put it in water, wait for it to saturate, then I place it on the model.
On the model itself, I paint gloss first, and let that dry.
Then I put a heavy coat of Micro-Set (the blue one) and while it is still wet I put the decal on the area.
I let that dry, add another coat of micro-set, and maybe micro-sol after that if it's being onery.
Once that's done, I coat it with gloss again. And once that drys I coat with a matte varnish.
I hope this helps!