Scrub it with a toilet brush, flush, add bleach, scrub it harder, flush. Make sure the brush is “clean” and drown it in bleach til next use. Use the flush stream to get “specs” off the toilet brush.

Also ypu can use those toilet cleaners that remove sarro, but I usually just use bleach.

I preffer to use “gel bleach” cuz less chance of droplets landing in your clothes or skin.

Oh, and for the outside, if it’s your home toilet and nothing terrible had happened to it, I just scrub it with detergent/soap and a “harsh” sponge I use only for cleaning the outside of the toilet.