Is it permissible to relieve sexual urges by pressing the thigh against the vulva after a wet dream, and is this considered masturbation? And how can one relieve sexual urges if this act is impermissible?

If the intent behind alleviating desire is to deliberately cause ejaculation by pressing on the vulva, then this falls under the ruling of forbidden masturbation. In this case, desire is alleviated by distracting oneself from it and diverting one's thoughts to worldly matters.

However, if the intent behind alleviating desire is merely to press on the vulva without intending pleasure or ejaculation, then there is no evidence to prohibit that.