shaving a bit off a laminate countertop
I did exactly this to fit a slightly bigger sink into an existing countertop made from laminated chipboard. The difference in size was very little (perhaps 5mm)

I used a cheap jigsaw - it was a struggle and the line was not straight but I managed to keep the top edge of the cut within my marked rectangle. Part of the problem was finding a long enough blade that would cut on the downstroke (since I only cared about breakout on the top, from where I was cutting).

I finished up and straightened the edges of the hole with a surform, a rasp and a coarse sanding plate (like coarse sand paper only made of very long-lasting metal, I happen to have one I bought decades ago).

Sanding is too slow.