Sforno on Genesis 48:10/ספורנו על בראשית מ״ח:י׳

1לא יוכל לראות, he could not see clearly. In order for a blessing to take hold it is necessary for the one bestowing the blessing to see the party whom he blesses at the time the blessing is pronounced. [the same is true of a curse, this is why Balak took Bileam to a vantage point from which he could see the people of Israel whom he had been hired to curse, clearly. (Numbers 23,13). G’d also took Moses to a point from which he could see the land of Israel clearly so that he could bless the land. Something similar occurred in Kings II 2,24 where Elisha turned around to face the lads mocking his baldness before he cursed them.

2וישק להם ויחבק להם, the physical contact was designed to make Yaakov more attached to them so that his blessing would be correspondingly more effective.