I have a medical issue where droplets of urine fall on my pants after urinating. I am worried about that the purity that my pants have would prevent me from doing salah.

What is the best way to practice istibra to prevent this?

How could I make my pants pure for salah? Especially when there might be a smell of urine?

Istibra is performed as follows:
After urinating, the anus is first purified if it has become impure; then, the middle finger of the left hand is slid three times from the anus up to the scrotum; then, the thumb is placed on the penis and the forefinger is placed under the penis, and the thumb and forefinger are pulled three times along the penis up to the point of circumcision; finally, the end of the penis is pressed three times.
However, if after istibra you are certain that the fluid came out of you is urine, then you have to wash it.