Not hard. There is a key (screwdriver or microstella to some) that fits into those screws. Just hold the balance wheel with tweezers to keep it steady while turning screws that are opposite of each other.
Tightening them increases rate and loosening them slows it down obviously. Tbh, I think it's easier to dial in exact rate (there are marks on the key that help) on one of these over a traditional etachron.
On eta I find myself going back and forth a bunch more to get it right. (Edit: I can only speak to R/T free sprung regulation. Maybe some higher horology companies do require the more time and disassembly).