For example an F1 labradoodle may or may not shed or (most likely) be somewhere in between - shedding some, but not as much as a normal lab.

Backcrossing that F1 with another poodle to get an F1B means you're nearly certain to get low- or no-shed. There's still exceptions (as with everything in life), but it's extremely rare to have a high-shed back-crossed mix.

And of course, if you want to further ensure no-shed (vs low-shed) you can go more generations or genetic test the coats of the parents. The only real question is how much that additional certainty is worth to you. At some point, the probability of low-/no-shed is generally high enough that people are OK taking on that bit of risk.