"unless you use FMJs or hard cast bullets".
That is why you use hard cast bullets. You can also use gas checks. I don't know if you can get them, but Hornady makes a .35 caliber gas check that seems to work fine in 9mm.
For those who are not familiar with gas checks, the main cause of lead fouling in barrels is not the friction of the bullet against the barrel but the hot propellant gas melting the base of the bullet. A gas check is a small copper, brass or aluminum cup that fits over the end of the bullet and is crimped on by the sizing die when the cast bullet is sized. Being between the hot gas and the lead bullet, it prevents the bullet base from melting and fouling the bore. It is best used, though, in conjunction with, not instead of, hard cast bullets.