There is saying that there is no such thing as a bad blow job. Well I disagree, I have had bad blow jobs and I can't even stay hard and of course it gets frustrating for both partners. I've also had blow jobs that were so good I thought I'd blow the back of their head off, lol. For your issue I'd just say honesty is your best bet, just tell them up front that oral isn't your thing, but let's do this or that instead. Good luck!

Of course it's ok.
Last time I was at a sauna there were about 4-5 guys in one of the rooms. We were all hard and I was in between two guys. One of them started jerking me off so I touched his cock too. The guy on the other side was playing with my nipples so I started jerking his cock with my other hand. He leaned over and wanted to suck but I said no and let him them both jerk me until I came.
I'm not sure if I got either of them to cum but I got up and left and saw them start to jerk together when I left.
So it's always ok to say no to that. Just take what you want. I'm sure they'd be ok with that too if they're there to see some cum.

Thanks for that advise guys. Sounds good.

I think Tomcat got it correct although I have never said no to a BJ. I was at a nude beach yesterday and got a great BJ and licking

is as tomcat says ..... at male sex camps and gay beaches i wood let men i was playing ith know that i save my penis just for my sex bud at home and my butt hole too .... butt .... am cool with sucking my nut sack or rubbing their penis on outside of my anus .... was down with that both ways.... i cum on guys butt cracks .....and they on me ...

nearly everyone i sexually interacted with in these setting has been fine with my boundaries ....... often was just him and me so in the woods or at my campsite ...... so wasn't any other selection butt me..... is so fun to do this....sex is so varying .... male on male or group gay couplings........ butt me, i m naked ..... cg

of course it is OK and no means no, always, mostly for me if I am being given a bad head job I go soft very quickly anyway and I just say to him "sorry mate, lost it, maybe some other time" then I pull my cock away and just move on