Manhaj - may Allaah bless you - is built upon the aqidah, so whoever's aqidah is sound, then his manhaj will be sound without doubt, because the Prophet (sallallaahu alayhi wasallam), when he mentioned the splittign of the Ummah into seventy-three sects, all of them in the Fire except for one, they (the Companions) said, "Which one is it O Messenger of Allaah?", and he replied:

Whoever is upon the like of I and my Companions are upon.

So his saying, "Whoever is upon the like of I and my Companions are upon", meaning in aqidah and in manhaj and in action, and in everything. And it is not possible for this (i.e. aqidah) and this (i.e. manhaj) to be divergent.

So for example, the Ikhwanis and Tablighis and Islahis and other than them, if their manhaj does not oppose the Sharee'ah, then there is no problem in it, and if it opposes the Sharee'ah, then it necessarily arises from (opposition in the) aqidah, because every action has an intention, and when a person takes a manhaj that opposes the manhaj of the Messenger (alayhis salaatu was salaam), and his rightly-guided Caliphs, then its meaning is that his aqidah is not sound. Otherwise, when the aqidah is sound, the manhaj too will be sound.

Source: Cassette: Liqaa al-Baab al-Maftooh (no. 128), also see here.

As for the manhaj of the Tabligh and Ikhwan and others, then the Scholars of Ahl us-Sunnah have pointed out thoroughly their errors in their aqidah, their understanding of Tawhid, and their methodologies in da'wah, and they have entered them into the ranks of the seventy-two groups threatened with Hellfire in the authentic texts.

Compare the above with what has been said by Shaykh Ubayd al-Jaabiree (hafidhahullaah) - which is documented in full here - as occurs in the cassette (الإيضاح والبيان في كشف بعض طرائق فرقة الإخوان ):

And Islaam is composed of these two: correctness in belief and soundness in manhaj (methodology), and its uprightness. One of them does not separate from the other. Thus, whoever's manhaj is corrupt, then have trust that it springs from corruption in his aqidah. So when the aqidah is upright upon the correct manner, then the manhaj will also be upright.