Ellie is having urine issues again. The vet did a u/a and culture a few weeks ago because she was going too much. Everything is fine. After her spay it got worse. Now it is better again but she did pee in her onesie last night an hour after going outside. THe vet asked if I wanted to bring urine in and I said no.

I am not going to keep doings u/a's if everything is fine. She said I could get pH strips and bring her in if something is wrong.
How do they work? Do you just hold them under the dog when they pee or do you have to dip them in a cup? I can't catch Ellie's urine in a cup. What about pH sticks? What is better?