Is there any point in a Kohen or a Bechor growing his thumbnail for the purpose of the Melika Avoda in the Beis HaMikdash?
Indeed, every effort should be made to prepare for the Yemos HaMoshiach. But in this specific case, this is the wrong approach.
Holy sefarim present serious matters about growing long nails (see Hebrew footnotes), and of course, the preparation for Yemos HaMoshiach should not come at the expense of other matters within the framework of “our deeds and our work throughout the duration of the exile” which bring us to the Geula.
Besides, we have never been commanded to do actions now in preparation for the days of Moshiach such as preparing a Korban Pesach and things like that. This approach comes from other circles and is not our way. Nor have we seen that Rabboseinu Nesieinu or the Gedolei Yisrael in general promoted such an approach.
The preparations we were commanded to do is to study portions of Torah dealing with Moshiach and Redemption, conducting ourselves in thought, speech and action, as appropriate for such special times.
We do find certain great Tzaddikim who stood ready at any moment with their walking stick, their shtreimel and the like, but this was due to the magnitude of their expectation of the coming of the Moshiach, and not as a “preparatory action” done as an end unto itself or worse yet, as an imitation of someone else…
Sources:
האם יש ענין שבכור שהוא לוי יגדל צפורן אגודלו לצורך עבודת המליקה?