Will pouring my piers and footings at once cause the base to overflow?

Hydrostatic pressure is going to be your biggest enemy here. Even with the dirt backfilled around the footers, that won't stop the concrete from seeking its own level. When you start filling a four-foot pier form, the weight of that wet mud is going to push down and force the concrete right out of the top of your footing like a volcano. Dirt helps with the lateral blowout at the base, but it does nothing for the vertical pressure pushing back up thru the open footing. Most guys avoid monolithic pours on these unless they have a very specific reason to do it. The best way to handle this is a **two-stage pour**. Fill your footings first, then take a break. You want that concrete to set up untill it’s about the consistency of stiff peanut butter. Depending on the temprature and the mix, that might take an hour or two. Once it can support the weight of the pier without flowing, you come back and fill the vertical forms. If you try to do it all in one shot with a standard 4-inch or 5-inch slump, you’re going to have a massive mess on your hands. You’d need a very dry, low-slump mix for the bottom and alot of patience. Even then, vibrating the pier can liquefy the footing concrete again and cause it to blow out. It’s a nightmare to clean up when you have wet concrete spilling over your forms and burying your red string line. Just make sure your rebar is tied well and sticking up into the pier area. You don't need to worry about a cold joint if you time it right, but even if you do, it's a footing—it’s not going anywhere. Save yourself the stress and tell the truck driver you need some time between the footings and the piers. Most of those drivers are used to it, or they'll just pour the footings a bit stiffer to help you out.

That peanut butter analogy makes sense, but I'm worried about the truck driver. If I tell him I need an hour or two for the footings to stiffen up, won't he get annoyed or charge me a ton for 'wait time'? I'm on a pretty tight budget for this project. Also, if I wait for it to set a bit, do I need to do anything to the surface so the pier acutally sticks to the footing? I've heard people talk about 'roughing up' the wet concrete with a tool to help the bond. Is that actually a thing or does the rebar do all the heavy lifting there?

You're right to worry about the clock. Most companies give you 45 to 60 minutes free before they start charging for wait time, and those fees rack up fast. To save cash, have the driver pour the footings with a realy stiff 2 or 3-inch slump first. It stays put better while you work. For the bond, just scratch some deep cross-hatches into the wet footing surface with a piece of rebar or a stick. That creates a mechanical 'key' so the pier stays locked in place. As long as you don't let it dry to a hard crust, you'll be fine.

If you're worried about those wait time fees, try cycling trough the site. Pour every footing first, then circle back to the start to fill the piers. Usually, by the time you've hit the last footing, the first one has stiffened up enugh to take the load. Just keep a close eye on the base as you fill the pier—if you see any oozing, move to the next one and let it rest for 15 minutes. It’s a bit of a juggle, but it beats paying the driver for sitting on his phone.

You gotta watch that red string line once the truck starts moving. The vibration from the engine alone can shake your stakes if the ground is loose. Keep a garden hose with a spray nozzle handy. If a little mud starts oozing out while you're filling the pier, you can wash it off the forms quickly. It keeps your wood cleats clean so you can acutally remove them later without chipping dried concrete. If you’re still worried about the bond, throw a handful of clean gravel onto the wet footing surface. It acts as a mechanical key for the pier to grab onto.