General synonyms:
* Skillfully
* Adeptly
* Expertly
* Nimbly
* Cleverly
* With ease
* With precision
More specific synonyms:
* With finesse: emphasizing elegance and grace
* With dexterity: emphasizing agility and manual skill
* With artistry: emphasizing creativity and artistic skill
* With dispatch: emphasizing speed and efficiency
* With aplomb: emphasizing confidence and composure
The best synonym for "deftly" will depend on the context of the sentence and the specific meaning you wish to convey.