The first few times i ever gave a guy a blow job I was a bit scared about my throat hurting and it tasting weird. I read online you can suck on a cough drop before and during blow jobs and it actually works. The cough drops will numb the back of your throat a little bit (to alleviate sore throats) which will make it so your throat doesnt hurt from sucking. Also, if you get some that taste good, it will mask the flavor of his penis. Also, maybe you could ask him to shower first, possibly being at work all day makes him taste bad. And if it is his cum you don't like the taste of then right as he is about to cum, go down on him as much as you can and let him ejaculate into the back of your throat and just keep swallowing. Be careful not to inhale though lol but that way you never actually taste his cum, you just swallow it.