Because I didn't have any extra money, I didn't. The exception was in 2015 when I had a 2nd FT job in a situation you'd read about in the Reddit forum "OverEmployed." While making an extra $3,500 a month, I put $1,000 into a 529 that grew to about $22,000 in 2020, and it got us through a couple years of tuition.
Now, I'm just paying for college as they go.
How do I do it?
1. My income is much higher now
2. I told the kids from a very young age to start at community college, and for years 3 and 4 to go to a state school so the credit transfer isn't an issue.
I currently have 1 in a local state school, and 1 in the community college where I teach (partially reimbursed tuition), who will likely dorm somewhere next year if she doesn't just start working.
ETA: I intend to write my kids a check for their weddings, and since there are 4 of them, it could possibly mean withdrawing from the penalty-free portion of my Roth IRA if they all get married close enough together.
Bottom Line: I don't have a fund of any kind for them. I make good money, am growing my retirement accounts, and am more likely to be mortgage-free because I downsize when my youngest finishes HS in 5 years.