I have used this power bottle brush for years 
https://www.ebay.com/itm/153676529158?hash=item23c7d5be06:g:jAcAAOS...

and this one too 
https://www.ebay.com/itm/274771391975?hash=item3ff9a6b5e7:g:Tk0AAOS...

they go on the end of your battery drill
Although, if there is stubborn reside, its best to soak them ovenight in mean green or simple green

I got one of these( KUWAN Bottle Cleaning Brush... https://www.amazon.com/dp/B06ZZ1R13N?ref=ppx_pop_mob_ap_share ) for my 32oz Spencer's lava lite brand lava lamp, it had cloudy master fluid I opened to filter it back clear and found the wax was a jelly type of texture when it was completely cooled down and it would not solidify. I heated it up with just the wax in the bottle and poured it out, then I used some isopropyl alcohol and the bottle brush to clean out the inside of the bottle, I alternated between the IPA and a liquid dish detergent with a little added sodium lauryl sulfate with 150°+ water to rinse the bottle out between cleaning solutions, I also washed the brush off separately so it wasn't just re-spreading the wax residue. After I felt like I had gotten the wax completely cleaned out of the bottle I rinsed it out with some acetone to make sure there was no wax or oils left on the bottle. Then I washed it again with soap rinsing it in progressively colder temperature water until it no longer made bubbles when it was shaken and pored out. After the bottle was air dried I added some sodium lauryl sulfate to recoat the glass surface to prevent future wax from sticking to the bottle.
The bottle brush is made out of a type of smooth foam cut and twisted around a flexible body kind of like a huge pipe cleaner made of craft foam type of material, instead of nylon bristles or coated sponge that doesn't work to scrub the inside surface and just pushes it around inside the bottle. It made it easy to clean the brush off so it wasn't re-depositing the wax being cleaned out/off.