Go for it! Saki Iiduka's book "Sashiko for Making & Mending" is my recommendation for finding a sashiko pattern, though there's plenty of other sources out there. Drawing a grid on the fabric can be tricky, but even if it's wobbly, the result is usually still fine.
Or use transfer paper or a heat-transfer pencil to get a pattern straight on the fabric.
One recommendation: don't try to use color, at least to begin with. Plain white thread usually gives the cleanest result.