Atáscate (ahora que hay lodo)

Atáscate ahora que hay lodo literally means 'get yourself all dirty now that there is plenty of mud.' It is used to indicate: (1) the opportunity that a person has to benefit from a situation (the mud is an allusion to something good to a pig); (2) the rather piggish behavior of a person in such situation. Sometimes the expression is shortened to ¡atáscate! 

Example:

Lic. Goicoechea: Acaban de nombrarme supervisor de permisos y licencias del municipio.
Amigo de la infancia: ¡Atáscate ahora que hay lodo!

Mr. Goicoechea: I was just appointed supervisor of permits and licenses of the city.
Childhood friend: This is your chance to profit big time from your position!