Whom did they appoint as a Shali'ach to approach Yosef on their behalf?
Rashi: They appointed the sons of Bilhah (Dan and Naftali) as Sheluchim. 1
Seforno: They commanded Ya'akov's servants or somebody else to go and speak to Yosef.
Rashbam: They commanded modest emissaries to speak to Yosef before they went in to speak to him.
Targum Yonasan: It was Bilhah whom they sent to speak to Yosef.
Since Yosef was friendly with them, as the Pasuk testifies in Vayeishev (37:2 [Rashi]). It is unclear why Rashi omits the sons of Zilpah (Gad and Asher), whom the Pasuk there includes.
Nowhere do we find that Ya'akov actually issued such a command!
Rashi: He didn't - because he did not suspect Yosef of planning revenge. It was the brothers who concocted it, with a view of making peace with Yosef.
Seforno: Although the Torah does not record it, Ya'akov (who did not himself suspect Yosef of such bad Midos) ordered the brothers to tell Yosef that he had ordered them to say the following, should they be afraid that he is planning revenge.
Why did Yosef weep as they spoke with him?
Seforno: He wept when they mentioned his father and the love he bore him, in that he did not suspect him of taking revenge.
Why did the brothers wait until after Yakov died before appeasing Yosef?
Da'as Zekenim: Initially, they thought that Yosef had forgotten the matter. There was no reason to arouse the hatred. When they returned from burying Yakov, they saw that he had not forgotten. Refer to 50:15:1:2.
רש"י: את בני בלהה: מנין לפרש כך?
גור אריה: לא מסתבר שהם גילו את סוד המכירה לאדם אחר.