Most stains like this when only a few days old can be removed with any pre spray with a low ph. Once they are older and set they are harder and need stronger chems such as rust remover or even oxidisers or reducing agents.
If the wilton is polyprop ( B/W) then sould come out with no probs using usual chem prespray, if wool then a different ball game and go with caution advising customer that it may be permanent or even you may not be able fully remove all the stain.
