Should I do two coats of Zinsser BIN Primer?

Should I do two coats of Zinsser BIN Primer? For most jobs, one coat of Zinsser B-I-N shellac primer is sufficient because it is very high hiding and strong stain and odor blocker. B-I-N is designed to block severe stains like smoke, fire, nicotine, pet urine, water stains, and tannin bleed in one coat, and its shellac formula seals effectively. However, two coats may be beneficial for extremely severe stains, heavy nicotine or fire damage where first coat still shows shadow, or when covering drastic color change, or for porous surfaces that absorb heavily. If after first coat you still see stain bleeding or odor, apply second coat after 45 minutes dry time. Second coat also improves uniformity for topcoat. For general priming over clean drywall or light stains, one coat is enough and saves money since B-I-N is expensive. Manufacturer recommends one coat for most applications. So evaluate after first coat, if stain is fully hidden and surface looks uniform white, you can topcoat, if not, do second coat. Avoid overly thick coats as shellac dries fast and can be brittle.