If by tasawwuf you mean the authentic Islamic spirituality, then a da`i who observes the method of the Prophet is practicing tasawwuf.

If, however, by tasawwuf you mean some kind of occult practices and initiation through a so called sheikh into some mysteries, then those are deviations and innovations, which we must avoid. They are far removed from the sound Islamic spirituality that is the quintessence of Islam.

Authentic tasawwuf consists primarily of interiorizing the authentic Islamic practices. This can be done by observing the following:

1) The first stage on the path of spiritual purification is repentance and sincerity of intention. Repent your sins sincerely and make it a consistent practice, then purify your intentions and motivations by critically examining each and everything you say or do.

2) Examine your faults and seek to correct them using every available means and method; it is a good idea to have a trusted friend to advise you of your own faults.

3) Keep the role model of the Prophet (peace and blessings be upon him) and emulate his examples as best as you can. Also converse with the righteous predecessors (that is, the earliest generations of Muslims) by reading their life stories.

4) Practice dhikr (remembrance of Allah) consistently by using the prescribed du`a’s(supplications) and the words of tasbih (the formulas for glorifying Allah).

5) If you find a scholar who is pious, then you should seek his advice and benefit from his knowledge and company as much as possible.

6) Manage your time wisely. Divide the hours and set aside time for solitude and self-scrutiny.

7) Read the Qur’an and listen to it as much as possible every day.

8) Make use of every opportunity you get to benefit people and Allah’s creation through compassionate deeds.

http://www.onislam.net/english/ask-the-scholar/dawah-principles/dawah-to-non-and-new-muslims/169576-should-the-daiyah-be-a-sufi.html?New_Muslims=

http://300035.dotdothktrade.tech/en/artical/26589/Should-Da`iyah-Be-Sufi