A hot ultrasonic with EC cleaner is the best way when you have a lot of flux that won't budge. Once it's out drown with 99% isopropyl and scrub with a fine toothbrush. Quality of the brush matters here, better ones make your job much easier. Personally I like brushes like these: https://www.amazon.com/dp/B07WDW3JM1/ref=cm_sw_r_cp_apa_fabc_1BZbGb27WR3N0?_encoding=UTF8&psc=1 Let the board dry either on a hot plate set to a warm temp or in a toaster oven at 200f or something. I like to set it for around an hour. Too much heat when drying can cause nasty issues. Should look factory new once complete.
NAD
I'm 30 years old and still have a lot of trouble consistently brushing my teeth. At the worst of times, I only brush my teeth maybe 4-5 times a YEAR (ADHD and bipolar disorder with long depressive episodes make it incredibly difficult to focus on self care). I didn't see a dentist for 5ish years. Bleeding gums is common after not brushing for a while. The important part is to try to keep yourself on track (use an app, sticky notes, write a reminder on your mirror with a dry erase marker, whatever you can do to remember to do it). I can't speak on what kind of dental work you might need though.
As another commenter said, focus on the future for now. Make an appointment with a dentist ASAP. If you haven't been for a while/it's a new dentist they'll likely do a thorough exam on your first visit and let you know what work needs to be done.
In the meantime, I might suggest getting an ultra soft bristle toothbrush (something like this ), it won't completely stop the gum bleeding, but it's not as abrasive so it will cut down on it a lot (as well as being less painful if your gums are sensitive)
Oh wow! That's some newfangled future stuff! Yeah she'd probably be into that with her fancy self but she's wanting this right now. It says the bristles are super soft, wondering howthat would help get plaque off.
I have sensitive teeth, so I use an extra soft toothbrush, but if you hate normal toothbrushes you could probably benefit from them too!
Amazon link and target link.
It looks like this
20,000 bristle toothbrush
https://www.amazon.com/dp/B07WDW3JM1/ref=cm_sw_r_cp_apa_i_zq5fFbDT1TZXB