How can a character escape after being engulfed by a shambling mound?

A shambling mound will be attacking the party I DM for during tonight’s session, and I am unsure about how to deal with the monster’s Engulf feature.

The shambling mound’s multiattack action states (MM p. 270):

The shambling mound makes two slam attacks. If both attacks hit a Medium or smaller target, the target is grappled (escape DC 14), and the shambling mound uses its Engulf on it.

So if both slam attacks hit the target, the target is grappled, and then the shambling mound immediately engulfs it. As I understand it, this all happens on the same turn, since it is part of the multiattack action.

The Engulf action states:

The shambling mound engulfs a Medium or smaller creature grappled by it. The engulfed target is blinded, restrained, and unable to breatheā€¦

How would the target escape once it is engulfed? The DC of 14 in the multiattack description is for escaping the grapple, does it also apply to escaping after being engulfed? Or would a contest make more sense (shambling mound’s strength vs. target’s strength/dexterity)?

Further complicating the matter is the fact that the target is blinded (automatically fails all ability checks relying on sight). Would being blinded impact the target’s ability to escape, e.g. would the target be so disoriented that it would not know which way is up or down without sight?