Yes, for longer performance of Bora-Care with Mold-Care, the product label states that exterior wood surfaces that have been treated will require a top coating with a water resistant finish such as paint or exterior stain. Apply the finish or topcoat within 6 weeks of treatment. It is important to allow treated wood to completely dry (at least 48 hours) before applying any protective topcoat. Coat a small section of treated wood with the finish to be used and check for compatibility prior to complete application.
Bora-Care with Mold-Care is meant to be used as a wood preservative and mold treatment for wood pieces only. It is not labeled for soil, so we cannot recommend it for that use. We do not sell any products that are labeled for mold on soil at this time.
We would recommend addressing the moisture and humidy levels in the crawl space to prevent futher mold from growing.
Per the manufacturer, it is confirmed that Bora-Care with Mold-Care will kill on contact however the water issue causing the mold/mildew needs to be fixed first.
Bora-Care with Mold-Care can not be foamed for mold and can only be applied a 1:1 ratio directly to the areas where mold and mildew are growing.
For removing musty odors associated with mold and mildew, Pyranha Odaway Odor Absorber would be a great option and comes in a Concentrate, a Ready To Spray Aerosol or Trigger Spray bottle.
The Bora-Care with Mold-Care label does not permit you to mix the product in the way you are describing. The manufacturer intends for this product to be mixed in 5 gallons of water all at one time. We are not permitted to give you off label mixing instructions. We apologize for this inconvenience.