Downhill is good for moving anything heavy. If the ground is lumpy or somewhat soft, lay some planks for a runway for the barrow. If not enough planks, have an assistant leapfrog the ones you have as you move the barrow. If you hire a mixer for DIY, remember you'll have to move the mixer back uphill to return it to the rental yard.
Of course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain