There is a
BIP 39 Spanish word list, but the words are not equivalent to those found on the English version, nor are they interchangeable.
As far as I understand, the only thing that is really important in those list of words is the number associated with the words.
For example, in the
BIP 39 Spanish word list the word carro is associated with the number (line) 351. The word Cloth in
English is also 351
So, he could just make a list of numbers associated with the words. In the end, the seed is just a combination of numbers as well.
Then, he could make something like this:
0001035100102048
which would translate to words:
0001 (abandon) 0351 (cloth) 0010 (abuse) 2048 (zoo)
Anyway, any of those methods don't really add any security, and saving the words just like the wallets recommends is the best.