Oversættelse - Dansk-Latin - Jeg er nu uddannet hundemassør

in canibus fricandis --> in canum fricando?

because "in canibus fricandis" can be read "in dogs who should be massaged"

I intended "fricandis" as a gerundivum pro gerundio. In this case the gerundivum has not the meaning of "must, have to".

"In canibus fricandis" --> "In canes fricando"

Yes, of course! "Fricare" is verbum transitivum, so should be "canes"! You're right, "in canes fricando" will be great.