Multi instruction for the aircraft class rating and the IR must be conducted by an approved FTO. You cannot do it as an individual instructor. He should be able to use his own aircraft. Stapleford use the DA42.
Now what is the question relating too, the student or the instructor?
The Multi Instructor course cannot be conducted on a DA42, it most be done on a 6 lever twin! You need 30 hours PIC on ME aeroplanes in order to do it.
The candidate needs 70 hours PIC before he can take a MEP Class rating Skill Test. He will need 50 hours navigation before he can do the IR and will need to have passed the IR exams.
If you want to train him for an IMC rating which you can do as a FI once he has a ME Class rating, then you will need a ME Instructor rating and familiarisation training on the DA42.