Why does Hashem refer to the craftsmen as 'wise-hearted men', something that He did not do with regard to the same men or even with Betzalel who built the Mishkan?
Oznayim la'Torah: Because, bearing in mind that the Tzitz had engraved on it "Kodesh la'Hashem, the Choshen contained in its folds the Urim ve'Tumim including the seventy-two letter Name of Hashem, which enabled the Kohen Gadol to attain levels of Ru'ach ha'Kodesh, the Bigdei Kehunah were on a higher plane of Kedushah than when they built the Mishkan, which meant that when manufacturing them, they required deeper Kavanos
Why did Hashem instruct Moshe personally to speak to the wise-hearted men who manufactured the Begadim?
Ramban #1: Refer to 27:20:3:2*.
Ramban #2: He was instructing Moshe to inform the workers that they should make the Begadim having their Kedushah in mind.
Seforno: He was instructing him to inform the workers to have in mind when manufacturing the Begadim, that the Begadim should sanctify Aharon .
Seeing as "Chachmei-Leiv" is plural,what is "Mileisiv" (singular) referring to?
Targum Onkelos: It translates as 'with each of whom I have filled with a sprit of wisdom'.
Targum Yonasan: Even though it is written in the singular, it refers to all the Chachmei-Leiv
This is also how the Ibn Ezra translates it.
What does the latter half of the Pasuk mean?
Rashi: It means that Aharon was to be sanctified as Kohen Gadol by wearing the Begadim 1 that are about to be listed, and that this, in turn, would enable him to serve as Kohen Gadol.
See also Pasuk 41, which implies that it was in conjunction with the anointing and the inaugural ceremony that the Begadim sanctified Aharon, as is described further in chapter 29.