When Captain Torres enters the barber shop, he says, "It's hot as hell." This is an example of overstatement. He says more than what is true in order to emphasize the truth: that it is incredibly and unbearably hot.
When the barber describes the sound the razor makes as it "rasped along" the captain's thick beard, he employs onomatopoeia. This is a word that actually reproduces or mimics the sound it describes. The word "rasp" is an example of this literary device, as we can certainly imagine the scratching, rasping sound of the razor blade over a four-day beard.
As the barber shaves the captain's neck, he considers how easily "One of the tiny pores could be opened up and issue its pearl of blood." This is a metaphor, a comparison of two unalike things where one is said to be the other, because a drop of blood is not literally a pearl. However, one drop could be similar in its round shape, and blood is certainly something of great value, like a beautiful pearl would be.
When the barber describes the waves of violence in the town, he thinks that "it goes on like this until everything is a sea of blood." This is another metaphor, comparing the amount of bloodshed to the water in an ocean, emphasizing just how prevalent the violence is.
Using another water comparison, a simile this time, the barber imagines what it would look like if he did cut Torres's throat, how the blood would "inch" along the floor "like a little scarlet stream." A simile compares two unalike things using the word "like" or "as."
Ultimately, the story ends with a significant irony. All along, the barber has believed that "Torres did not know that [the barber] was his enemy. ... It was a secret shared by very few, precisely so that [the barber] could inform the revolutionaries of what Torres was doing in the town." Torres's relaxed behavior in the barber's chair would seem to confirm this. However, as Torres leaves the shop, he says, "They told me that you'd kill me. I came to find out." Thus, situational irony is created, as what we expected is not actually what happens. All along, the reader feels the tension created by what seems like dramatic irony, as we think we know more than Torres and that he is unaware of the threat the barber poses to him. However, we now realized that he did know, and this irony is shocking.
In "Just Lather, That's All," the author uses a number of literary devices. Firstly, he uses a simile to describe the glide of the razor:
The skin would give way like silk, like rubber, like the strop.
A simile is also used when the Captain is talking about the heat of the day. He says, for example, that it is "hot as hell."
The author also uses onomatopoeia in the phrase, "Zip! Zip!" to describe how easy it would be for the razor to slit the Captain's throat. This creates an auditory image in the reader's mind, giving the reader a sense of what this action might sound like.
The author also uses the razor as a metaphor for the barber's dilemma. Just as the razor can be used for good or evil, the barber can either kill the Captain and become a murderer, or he can simply do his job by giving the Captain a shave.
Let's begin by looking at the first thing that Captain Torres says. His excalmation that it is "as hot as hell," is both a simile and an example of hyperbole. Clearly it is not literally as hot as hell, but his simile helps express the intense heat he feels. Later on, as the Baber internally debates whether he should kill Captain Torres or not, note what he says:
No one deserves to have someone else make the sacrifice of becoming a murderer. What do you gain by it? Nothing. Others come along and still others, and the first ones kill the second ones, and they the next ones--and it goes on like this until everything is a sea of blood.
This last phrase, "everything is a sea of blood," is actually a metaphor, as it compares this situation of unrestrained vengeance to a sea of blood to emphasises the slaughter and bloodletting that would occur in such a scenario. It is a metaphor because this comparison is directly asserted, without the words "like" or "as."
A simile is used to describe the blood that would emerge from Captain Torres if he did kill him. The Barber says that so much blood would come from his body that it would leave the shop and reach the street "like a scarlet stream," obviously emphasising the quantity of blood that would emerge from Torres.
So, there are a few examples. Now you can go back and re-read the book and hopefully identify a few more. Good luck!