Out of flaked shellac, not much will (should) come out, other than undissolved clumps of shellac--there always seems to be some--but other types of shellac, particularly button or stick, will have bug bits in them.
After all, it is an all-natural(tm) product.
You even really should strain pre-mixed stuff, since it typically has clumps, too. You can find medium and fine strainers that work well in the paint department of box stores.