Nothing more involved than cutting your ingredients to fit. With a 1.5 gallon jug, you'll probably want to aim for 1 gallon batches, so cut everything by 5.
Timing, temperatures, etc. all stay the same.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk