I use a small screwdriver or chisel tip on the iron, 700 deg F calibrated with a Hakko clone thermocouple. I use whatever solder Joe recommended way in back, probably what you use.
On the control board, I solder the backside with the small screwdriver tip. Then move to the top and very carefully touchup the top being very careful with the heat. I'll switch to a long conical SMD tip to reach under plastic transistors or or tight places. That long SMD tip doesn't carry much thermal mass heat so there's little chance of heat stressing the component. After doing SMD projects on hot plates, ovens, and hot air, lightly neatening up the top of the board using good judgement and proper tip/temperature isn't a issue to me
On the backplanes, the PEM nuts are easy to due with a good iron and a screwdriver tip. Long ago Joe posted about spinning the PEM nut with the tip while adding solder. This works great once everything is up to heat and there's liquid solder between the board and nut, just have to be aware the nut has to be square with the board as it cools. I aim for good solder penetration and a nice raised solder "doughnut" on the bottom of the board. Then run a tap through the nuts and lightly lube the threads. This pays off big time when installing the outputs. Once those silpads start to curl on the edge or wrinkle, stop.
The big things are, read old posts, intently study the photos, have the tools and parts, study the PDFs and print them if you need to or work off a laptop. Really study what prior builders did for success, especially photos. Have a good well lit workspace where you can work long term. And don't rush it. The first build can be intimidating, but once done, many of us build more these. They're really not that hard because Joe has made it easy with his outstanding kits.