But you know many women cannot orgasm by intercourse alone, of course. So helping her along is sinful? Or am I misinterpreting and it is not sinful as long as the man ejaculates inside her after her orgasm?
With their current partner's incompetence ... but I digress. However, far too many women are told they are "frigid" or have a low sex drive when in reality what they have is a spouse very poor at lovemaking and perhaps too focused on their own pleasure.
So helping her along is sinful?
No, it is perfectly acceptable.
Or am I misinterpreting and it is not sinful as long as the man ejaculates inside her after her orgasm?
There is nothing wrong with oral (or manual) sexual stimulation for a female either before or after sexual intercourse where the man has or will climax inside her.
Female oral sex is only sinful if it is seperated from the completed sexual act and is made into a solitary act of its own. One is not permitted to enjoy female oral sex during fertile periods as a substitute for sexual intercourse.
The same cannot be said about male oral sex. Male oral sex is always wrong because the sine qua non of sexual activity is the man climaxing inside the woman's vagina. So for him to climax in her mouth is inherently perverted. Because of the excitability of many men, even the use of this as a pre-intercourse stimulative technique is highly dubious because of the risk of pollution.
It would also seem that a woman is permitted to enjoy multiple orgasms both vaginally, orally, or a combination of the two, since the female orgasm does not end the sexual act, unlike the male orgasm. OTOH, the practice of some men with a high sexual drive of achieving multiple orgasms is inherently contraceptive unless the first is achieved vaginally, since nearly all the sperm are sent forth in the first male climax. So it would seem okay for a woman to achieve an orgasm orally and then another vaginally, but it is not okay for a man to do so.