I am Hungarian.

I used an online text to speech service (Mikropuhe Live) to listen to the pronunciation of the word.
The Finnish "ä" is sounds like the Hungarian "á", the Finnish "s" is sounds like the English "s" in most cases, the Finnish "i" is sounds like the Hungarian "é" and the rest of the word is pronunced phonetically.
Based on the pronunciation of the word, we (the Hungarians) would wrote the "s" as "sz" in this case.
The Hungarian pronunciation of the "s" is sounds like the "s" in the English "Sugar" word.

The Räkättirastas would be Rákáttérasztasz.
So it's indeed easy. At least for me.