Maybe by is thinking of daub not dob? Atomica gives lots of cheerful definitions, which sort of fit the idea, though they seem to refer specifically to paint:
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daub (dôb)
v., daubed, daub·ing, daubs.
v.tr.
To cover or smear with a soft adhesive substance such as plaster, grease, or mud.
To apply paint to (a surface) with hasty or crude strokes.
To apply with quick or crude strokes: daubed glue on the paper.
v.intr.
To apply paint or coloring with crude, unskillful strokes.
To make crude or amateurish paintings.
To daub a sticky material.
n.
The act or a stroke of daubing.
A soft adhesive coating material such as plaster, grease, or mud.
Matter daubed on.
A crude, amateurish painting or picture.
[Middle English dauben, from Old French dauber, from Latin d?alb?re, to whitewash : d?-, intensive pref.; see de? + albus, white.]
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And for me, a dollop always involves a spoon. It's the amount of something goopy you can scoop with a spoon, and with a flourish, glob it onto your plate. Therefore, as stated earlier, you couldn't speak of a dollop of orange juice. We would like use the word for sour cream or whipped cream.
