So I finally pulled the trigger and upgraded to a Canon 5D Mark IV after shooting with my trusty Mark II for nearly a decade and man I feel like a total noob right now because half my old gear isn't cutting it. I have a wedding coming up in Seattle in exactly two weeks and the weather forecast is already looking pretty dismal so I'm panicking a bit about getting this rig fully field-ready. I thought I could just swap my old cards and batteries over but the performance is just not there. The write speeds on my old CF cards are dragging so hard when I try to test the burst mode and the 4K video just stops after like five seconds because the buffer gets choked out and it's honestly stressing me out.

I only have about $800 left in my gear budget for the month so I really need to prioritize the absolute essentials to make sure I don't have a gear failure mid-ceremony. I noticed the battery drain is way more aggressive than my old body especially with the GPS and the dual pixel AF running all the time. Is it better to just buy a mountain of LP-E6N batteries or should I suck it up and get the battery grip? My hands are pretty big so the ergonomics might be better anyway but I'm worried about the extra weight during a 10 hour day.

Here is what I think I need to figure out fast:

• Memory cards that actually handle the 4K internal recording without dying
• A reliable way to handle the power drain for long shoots
• Some kind of rain protection that doesn't make the buttons impossible to reach
• A faster way to offload files because these RAWs are huge and my old reader is slow
• Maybe a screen protector for the touch interface?

I'm also really confused about the dual slot setup for redundancy because I've heard some people say the SD slot is way slower than the CF slot and it slows down the whole camera if you write to both at once? That sounds like a nightmare for a wedding if I lose speed but I need that backup copy for peace of mind. If anyone has a specific setup they swear by for professional work with this specific body let me know because I'm running out of time to order stuff...