One of the functions of the pubococcygeus (PC) muscles (there are two, one on each side) is to pull in the rectum/anus after a bowel movement. If you're contracting things hard enough to feel it in your anus, then you're contracting the PC. Try a few very slow contractions and stop just before the anus starts to contract.
For BC (bulbocavernosus) muscle, try to feel the contraction coming closer to the base of your penis. When I contract that muscle, I even feel some nice sensation flowing inside my penis, maybe this is blood or just the feeling of the contraction. You just need to contract soft for this, nothing hard is needed.
Do them whilst erect. That will make all the difference in being able to separate the two. It is good to occasionally work your PC muscle as well, as it helps with bowel movements. Using the PC to repeatedly squeeze the turd thinner whilst it is at the entrance of the asshole, then pull it back in, then push it to the entrance again whilst squeezing it thinner, really helps it come out. There is nothing worse than a big painful brick that won't come out! It isn't pretty, but it is reality. I guess it doesn't really matter what you call the muscle you contract when doing Kegel exercise, as long as you do it correctly and consistently. However, being a stickler for accuracy, I have to point out that men contract a different muscle than women when doing Kegel and it isn't the PC; it's actually the BC. This is probably the only place on the Internet where you'll find this distinction. Most will probably find it easier to "go with the flow" and conform to years of misconception by just calling it the PC.
Why isn't it the same muscle? Men and women are different. Females have essentially internal sex organs, males essentially external. PC muscle isn't the main muscle being exercised when men do Kegel. Of course men can contract their PC muscles. They do it every time they have a bowel movement. Some probably contract it while doing the Kegel exercise (by involving the anal area), but it isn't necessary to do so for a stronger penis.
women are much more in contact with the PC than the urethra is in men. In addition to forming a sling around the rectum, the PC passes by the sides of and inserts into the vagina and urethra in women. The contractions of the muscle can be felt by a finger in the vagina. This is why Dr. Kegel advised his female patients (he was a gynecologist) to exercise the PC muscle. It helps tighten the vaginal canal, rectum, and urethra, especially in women who have had children which can stretch these pelvic structures and cause urinary incontinence and uterine prolapse. Dr. Kegel showed that exercising the PC muscle could strengthen the female perineum and help cure the physical ailments as well as improve their sex lives.
Where is the bulbocavernosus (BC) muscle? Both sexes have a pair of BC muscles. In females it surrounds the vaginal opening. Some women can independently contract the BC and the PC. Most contract both at the same time. In the male, the two halves of the BC are joined in a "herringbone" pattern surrounding the bulb of the penis (the internal base of the corpus spongiosum).
The BC muscle has two main purposes. One is to force liquid (urine or semen) out of the urethra. It does this by way of the herringbone interlacing of muscle fibers which, as they contract, milk the urethra toward the meatus (opening at the tip of the glans). It also causes the penis to be pulled into the body. This happens every time a man urinates. It also happens with much greater force, and with rhythmic contractions, when he ejaculates. The BC muscle is the main ejector of semen. This is why ejaculation improves by exercising it.
The other function is to squeeze blood into the corpus spongiosum and the glans. The bulb of the penis is a reservoir of blood. At the time of greatest arousal voluntary or reflex contractions of the BC and Ischiocavernosus muscles force blood into the corpora. The Ischiocavernosus muscles surround the crura of the penis (legs of the corpora cavernosa). With both sets of muscles contracting on the base and legs of the penis, a maximum erection is achieved.
Locating the BC - the old adage about stopping the flow of urine is valid in locating the BC muscle in men. Even though the urethra does have a sphincter (just below the prostate) to stop urine flow, contraction of the BC will "milk" the urethra and let the man know which muscle to use for Kegel exercise. The BC muscle can also be felt with the fingers by placing them between the scrotum and the anus. Contractions felt through the skin at this point (in the midline) are from the BC muscle. The illustration PC or BC shows the relationship of the PC muscle in men as it passes by the prostate and surrounds the rectum. A strong BC muscle will not make you ejaculate faster. There isn't any relationship between the BC and the prostate.
Note: The urethra is the urinary tube passing from the bladder to the tip of the penis. It is encircled by the prostate gland and runs through the corpus spongiosum on the underside of the penis.