If you use a moderate temperature (650°F/340°C) it's a gentler way to clean flux residue off the tip.
Brass wool I reserve for scrubbing oxidation off the tip, but this eventually wears through the plating so I don't do this often.
Leaded solder is both toxic and completely unnecessary for hobbyist use. I like SAC305 but SN99.7 works well too—the key is a good quality flux core.
No-clean flux is convenient but if you do want to clean it, it's gummy and makes a mess. "Yes-clean" flux leaves conductive residue so it must be cleaned, but it is easier to clean.
As far as temperature goes, the better your iron is at transferring heat, the lower the tip temperature you can use, which improves tip life and, as you mention, reduces the chance of part damage.
I am a lead dev on an open-source hardware project (PhobGCC) and I've seen damage caused by bad soldering irons time and time again. Don't cheap out. I recommend a Weller WE1010.
I am cleaning my JBC tips with brass for the past 5 years of intense use and can't really tell a difference.
When using the brass wool, I tend to lightly rest the tip in a clean area. Maybe sometimes I will rotate it a few times, but I never use pressure or make wiping or scrubbing motions. I'm not sure if it really matters though (ie. how do the hardness of the tip plating and the brass compare?).
Flux - hobbyists either try to use 50-year-old parts with totally oxidized plating and no flux, or they use too much flux. New parts should not need more flux than you have in your flux-core solder or in your paste.
The next thing that happens after people discover flux is that they want to clean it off, and 99% of the time, hobbyists should not be cleaning flux. If you cannot measure the reason for cleaning your board, leave it alone. The manufacturers will tell you that modern RA and RMA type fluxes do not require cleaning for "most applications" - and "most applications" almost certainly means you.
No-clean flux should be called "never-clean" for the reason you outline. You shouldn't try to clean it, and it will never get as clean as you'd like if you do. I like no-clean for stuff I'm going to show to other people. You will almost certainly use no-clean in production if you go to production.
Water-clean is lovely stuff but it's very unforgiving. It will corrode if not cleaned, and you have to plan to wash your board by using sealed parts or adding water-sensitive parts afterward. You have to be careful with tip temperature too or it will destroy your tips. I have a spool of 63/37 water-clean I've used maybe twice - the boards sparkled but it was just too much trouble.
But yes, no-clean flux is best left where it is.
Depends on what you mean by "yes-clean" though - "water-clean" OA flux must absolutely be cleaned - it can start to corrode overnight even.
Makers come to our discord chat, asking why their builds aren't working and post a pictures.
I suggest cleaning the flux off, and they start functioning.
As an aside:
My current solder brand (Chip Quik) has a "no-clean water-soluble" flux that I'm curious about. Surely that's not going to be as corrosive as the flux you're talking about. (I probably wouldn't use it myself because it needs 140°F water to dissolve)
"No-clean water soluble" is news to me. Don't know if I'd trust that in a humid environment.
My budget is more in the $20 - $25 range. Cheap adjustable-temp soldering irons are available for under $4 [0], surely there is some middle ground between those irons and the $115 unit you suggest?
The $25 Pinecil sounds good and is probably your best option. I may go for soldering station since I can afford it.
Thank you.
The middle ground is the Pinecil, which is $25 but needs a laptop power supply.
It's… okay. It has less than half the heat transfer rate compared to the Weller, but it at least won't burn pads off your PCB.
Does SAC305 (for example) flow and cool in a similar way to good old 63/37?
So it takes a smidge longer to heat a joint than for leaded, but you don't need to hold the heat there as long once it flows.
It's slightly not eutectic, though, so you must immobilize parts as the joint solidifies.
Sn99.7 is eutectic but has a still higher melting point.
I find SAC305 to solder well at 340°C/650°F.