I have built the Robo-tank Pi4 controller, having never built a circuit board in my life.
So this was a learning thing, a friend said... FLUX... so I purchased Rosin soldering flux, apply the flux where you want to solder, hit it with the soldering iron, add solder, easy as. Soo much easier with flux. And yes there are many options, just ask for electronic soldering flux. They say no need to clean up the flux, but I like to and use CRC contact cleaner.
Really nothing to it... looks harder than it is.
Being old and blind and p-issed LOL, it can be hard to see so I use a magnifying glass... do not normally wear glasses but can not see FA up close.
Building a power box... OH and I should add... my tip for holding things when you solder them is tape, insulation tape. Works great. Put the part on the board, tape it down and solder a part, adjust if needed, (not often) and your good to go.
I had a small soldering iron (10w), worked out it did not produce enough heat, so this new one, was cheap 40watt and came with a light for my blind, p-issed old eyes! After soldering a joint you want to see a nice shinny joint. Not a dull joint, which could COULD be a cold joint and cause problems.
Add flux, heat part and add solder, clean up... that is my experience which is very / to none but seemed to work.
I had a friend who know his s-hit check my soldering and he fixed some joints on the PI4 board as my old soldering iron was not heating enough. Yes
Old (new) - iron... told that is what you want.. LOL -Not - 10watt. - just does the does the job at full power.. most likely i will never use it again.
Only thing this it is good for is teenage pimples popping... my 17yr old pizza head would not let me near..lol
Enter new, more powerful option with LED lights... what more could you wish for?
and here is where I am at, building a power box...
and parts....3D printed.. 2 sets for $80 from a reefer. Cases not perfect but OK.. took 14hrs for the main top each.