Sentence:  The undermakeup (<WSD>primer</WSD>) should be allowed to dry-set for 30 seconds. Apply foundation over the <WSD>primer</WSD> with a sponge using light, careful strokes to blend. Undermakeups come in cream form, sponge-on wands, or sponge-on cream, and as a lotion. 
Meaning of the word marked with <WSD> tags:  A layer of makeup that goes beneath the foundation; undermakeup.