It effectively bounces the paint back as it causes a back pressure thus leaving a thinner layer of paint. Doesn't always work but saves having too hard a paint line and a lot of compounding.
the pillar its self after 2/3 days depending on heat. drying times are given at 20'C which is regarded as bodyshop temp. The blend, i would leave a couple of weeks to really harden or you may form a hard edge.
