Yes, after using an etching stain, you MUST use an etching stain sealer that is suitable for garage use. The stain is not supposed to be eve, however most of the staining you see here in AZ is nothing more than an acrylic waterborne stain and sealer, not an etching stain. The only real etching stain on the market that you can buy at a big box retail store is from Valspar's Quikrete line of products carried by Lowe's. It's unfortunate that Lowe's cannot bring this to the market here in AZ.
You can do things like these with an acid etching stain:
This star was created using etching stains