We are planning on installing peel and stick planks over our existing engineered hardwood floor. Would this product help insure good adhesion?

Thanks for the question. When it comes to installing peel and stick planks directly over the TEC Skill Set Multipurpose Primer, that should only be done when the Primer is diluted and applied to a porous substrate. The Primer over an engineered wood floor will not bring a benefit to the bond of a peel and stick.