How does Winston Groom use imagery in Forrest Gump?

Imagery:

"Now I'm slow—I'll grant you that, but I'm probly a lot brighter than folks think, cause what goes on in my mind is a sight different than what folks see. For instance, I can think things pretty good, but when I got to try sayin or writin them, it kinda come out like jello or somethin.

" 'What is that?' the sergeant axed. 'Is you cookin somethin in that boiler!'
" 'That is the supper,' I says, an the sergeant got this real amazed look on his face, an a secont later, he got a real frightened look, like you might get jus before an automobile wreck, an then the boiler blew up.
"I am not exactly sure what happened nex. I do remember that it blowed the roof off the mess hall an blowed all the winders out an the doors too.
"It blowed the dishwasher guy right thru a wall, an the guy what was stackin plates jus took off up in the air, sort of like Rocket Man.