What’s the quality of your banger? Typically you should have a quartz banger that isn’t too inexpensive, otherwise you will never get that burnt stuff out. You pay for what you get essentially. Otherwise, iso alcohol and salt is the way to go. If you want a product I use this all the time: Formula 420 Glass Metal Ceramic Pipe Cleaner 12 Oz Bottles 4 Pack https://www.amazon.com/dp/B00O5E3XI8/ref=cm_sw_r_cp_api_glc_i_FT8ZFbFW6P7XM Hope this helps!
Not an ad, but I've had some success with Formula 420; I imagine any isopropyl alcohol with an abrasive like it has with do. It's a bit hard to get everything out though.
Ultimately, I just throw these out and end up getting an ol' reliable beaker bong, as it's always the easiest to clean. The experience of the perc is not worth the inconvenience of cleaning it.
Formula 420 Lot de 4 flacons de nettoyant pour tuyaux en verre et céramique 355 ml https://www.amazon.ca/dp/B00O5E3XI8/ref=cm_sw_r_apan_glt_i_6BBXQX29RQBH1BH3QB99
Isopropyl alcohol and rock salt. Or I recommend formula 420
These are awesome! I’m just going to leave this here….
https://www.amazon.com/dp/B00O5E3XI8/ref=cm_sw_r_cp_api_glt_fabc_25GY38M1Z1RDPM2P267K
Formula 420 on Amazon. Ships in a week