As the air moves through the lines it starts to cool, leaving condensation behind. Inspect the wood for flaws prior to each coat. By reflecting a bright work light at an angle on your product, you can see dried assembly glue, sanding marks, and dents before staining. Any imperfections you find prior to staining, sealing and top-coating will save the immense amount of labor involved in sanding or stripping the mistakes out later. If a coating says to agitate prior to spraying, agitate during spraying.
Stains have pigments that can settle out quickly, especially in dark colors.
Coatings contain sanding or flatting agents that will also settle. If you don't constantly agitate the coatings, your final colors and sheen may vary. Attend as many seminars on finishing as possible. Try to tap the knowledge that suppliers offer in as many ways as possible. Try new products on non-production pieces, dabble in marbleizing, faux finishes, dye stains, glazes and fillers.