Scuffing paint before sec. coat

I have never used Valspar or IH paint so I can't address the specifics. However, I'll add to what CNKS says with some comments. I assume you are reading the can label when you say "It says to put a second coat on after 48 hours". Does it actually say to put a second coat on after 48 hours or that another coat may be put on after 48 hours. And is the wording specifically for the use with a hardener. There is a big difference if a hardener is not used. Many enamels used without hardener cannot be recoated soon after the intial dry without wrinkling and lifting of the preceeding paint film. The time to wait to avoid wrinkling can vary from a number of hours to several months, depending on the actual paint and solvents used. I suspect, but don't know, that the 48 hours you mention is a minimum waiting period for recoating when not using a hardener. I consider it unusual for any enamel paint to instruct the user to apply a second coat after 48 hours as a matter of standard recommended practice without additional information. From what I have seen and read about Valspar, they are short on specifics and confusing in their recommendations. As CNKS indicates, the only real reason for applying more paint after an intial dry is to correct problems. The idea or practice of applying additonal coats "later" without scuffing up the surface with either sandpaper or Scotch-Brite is a poor one that can lead to poor relative adhesion between coats. I'd try to put Valspar on the spot for a better definition of how to use their paint if you can find a way to contact them. Lacking that, I'd always scuff for additional paint, hardener or not.

Rod

On thing that should probably be mentioned in this thread is the use of the terms "coat" and "recoat". I believe the term coat is used for successive applications of paint with only short times (minutes) between them. A typical paint film represents two or three such coats. Each of these coats is applied before the preceeding one is dry. The term recoat is generally used to mean application of additional paint after the preceeding paint film has dried (even though it is not fully cured).