What techniques does Hemingway use to project themes in "A Clean, Well-Lighted Place"?

Hemingway's story can be read as having an existentialist theme that life has no prescribed meaning and is not directed by a divine force. Any meaning that our lives have is a product of our own efforts.  

The old man drinks in the cafe to cope with his own existential fears. Though he interacts with others only minimally, he prefers to drink in a public place rather than at home by himself. His characterization (of civility and dignity) reinforces this idea:

The old man stood up, slowly counted the saucers, took a leather coin purse from his pocket and paid for the drinks, leaving half a peseta tip. The waiter watched him go down the street, a very old man walking unsteadily but with dignity.

The contrasting characterizations of the two waiters demonstrate how they bring meaning to their own lives. The young waiter is in a hurry to get home to his wife; the other waiter, who is older, is unhurried and obviously feels sympathy for the old man. His interior monologue about "nada" demonstrates that he understands that life on its own is nothing. To the older waiter, showing the old man kindness or sympathy is meaningful.

The setting of a "clean, well-lighted place" is impersonal; it can only become a symbol of something more than that if its patrons deem it so.

Does Hemingway use personal experiences to capture controversial themes in "A Clean, Well-Lighted Place"?

This is a dangerous question in that it assumes that the action taking place in the story is autobiographical to the author. That said, you can argue that Ernest Hemingway draws on his experiences in The Great War (World War I to most of us) to examine the nihilistic themes present in this story.

The story's climactic moment comes when the older waiter, who has been patient with the old deaf man who had tried to commit suicide the previous week, is having a drink of his own and recites his version of "The Lord's Prayer." The older waiter, who we can assume either served in The Great War or was at least affected by it, replaces most of the meaningful words with "nada," which is Spanish for "nothing." Here's an example (the replaced words are in brackets): 

"Our nada [Father] who art in nada [heaven], nada [hallowed] be thy name thy kingdom nada [come] thy will be nada [done] in nada [earth] as it is in nada [heaven]..."

Hemingway, who served in The Great War, often writes about the emptiness of the war and the feelings of hopelessness that came as a result. The war is what inspired thousands of Americans, Hemingway included, to flee the United States to live as disillusioned expatriates in France drinking much of their time away. It is what led Hemingway to write The Sun Also Rises, a novel about Americans disillusioned after The Great War. It is often considered Hemingway's most autobiographical work of fiction.

These themes of disillusionment and hopelessness that Hemingway explores in "A Clean, Well-Lighted Place" definitely shares some autobiographical roots with Hemingway, but, more importantly, they explore the themes predominant in the era immediately following the war.