Rear curtain flash every time. Keep the ISO high and the shutter relatively slow to keep some ambient/background light in, this also helps keep the flash output low so that it doesn't annoy people or burn through your batteries too fast.
dbltax
Just use the Brenizer method.
SD cards definitely seem to be a lot more unreliable than other standards such as CFe. Always shoot to two card slots simultaneously if it's for work.
The most cost effective way would be to buy a proper scanner second hand and do it yourself. It takes a long time, but once you're finished you can sell the scanner for about the same price that you bought it for.
Using a dedicated scanning service would save time, but cost a lot of money if there are a lot of photos.
If you've never used a supertelephoto prime then you'll have a hard time believing just how good they are. The optical designs are incredibly sharp, offer fantastic contrast and colour reproduction, as well as having almost zero distortion.
And no, their photos don't look borderline fake.
Use flash, simple.
Don't use LED panels for stills, they're just invasive at low light events. I've seen photographers use them in the evenings while shooting weddings, they just blind guests and give a very harsh and difficult to control light compared to a speedlight.
If you want to move into shooting weddings, then the best advice is to assist or second-shoot for an established wedding photographer. It's the best way to learn the ropes and get a feel for how they work and what's expected without having the pressure of being ultimately responsible for delivering the final results.
Method? Most likely Giclee printing, on a heavyweight conservation grade paper such as Baryta or Somerset Velvet.
It gets quite pricey at larger sizes, so much so that we ended up buying a couple of large format Epson Giclee printers that take 42" wide rolls of paper as it worked out cheaper in the long run than using a lab. Also meant that we can run our own in house calibration to ensure perfect colour consistency.
Much the same way that smaller photos are, just on a larger scale with heavier duty materials that are exponentially more expensive as they still have to be pH neutral and reversible so as not to damage the print.
Any works on paper should always be hinged from the top between a mount and undermount, essentially an acid-free barrier in front and behind the artwork/photo. Any tape should be acid-free and reversible too. Here's a good example pic to illustrate.
Like I said, the main difference is the size/cost. A regular sheet of mountboard costs me around £6 for a 44" x 32" sheet. Meanwhile a 104" x 60" 4-ply cotton museum board costs me about £133. That's literally just the cost price of a single sheet of mountboard, before you've even considered the rest of the frame, glass etc or the labour costs.