Depends what you mean by 'dual rated' as no 'rating' is involved.
FCL.900 Instructor Certificates
(c) Instruction outside the territory of the Member States:
(1) Notwithstanding paragraph (a), in the case of flight instruction provided in an ATO located outside the territory of the Member States, the competent authority may issue an instructor certificate to an applicant holding a pilot licence issued by a third country in accordance with Annex 1 to the Chicago Convention, provided that the applicant:
(i) holds at least an equivalent licence, rating, or certificate to the one for which they are authorised to instruct and in any case at least a CPL;
(ii) complies with the requirements established in this Subpart for the issue of the relevant instructor certificate;
(iii) demonstrates to the competent authority an adequate level of knowledge of European aviation safety rules to be able to exercise instructional privileges in accordance with this Part.
(2) The certificate shall be limited to providing flight instruction:
(i) in ATOs located outside the territory of the Member States;
(ii) to student pilots who have sufficient knowledge of the language in which flight instruction is given.
In other words, you will have to complete an approved FI course and pass an Assessment of Competence with an FIE, which will include a demonstration of familiarity with the EASA rules. Depending on the competent authority providing oversight, abridgement of the FI course may be possible (e.g. the UK Alt AMC reduces the training requirement to 30 hrs ground and 15 hours flight).