How you wanna do a 180 ollie to big spin is for starters, know how to do a 180 ollie. You can do a half can in either direction, but once you do learn how to do those, you wanna line yourself up, take some time, think about doing the big spin before you set it up. What you're gonna wanna make sure you do, is your foot lands the 180 ollie right on the tail so you can get that leverage to toss the big spin. As you do that, you're gonna turn your shoulders, get some momentum with your arms, you wanna nail the landing right over the bolts as usual, but it's also very important that you have enough space when you're doing that 180 and enough speed to actually kick it off with the big spin.
Now, as you do the big spin, it's not too dissimilar from a 360 shove it but this time, it's backside. So, what you wanna do is make sure you get that turn, you're comfortable with big spins in the first place, as well as being comfortable with the 180 ollie. Now also, it's very important you have enough speed to rotate. So, that's why using your arms to get that momentum that you want to actually land the big spin. So, when you land the 180, you gotta have in mind that you're gonna go straight to a big spin afterwards. It's tough to set it up, but once you do it, it's gonna be very rewarding. And that's how you do a 180 ollie to big spin.