What worked for me was putting the pad by the back door where Lady goes to bark to go out. At first she would bark and carry on and hold it as long as she could, but when she couldn't hold it any longer, she'd go. If you are right there, give her a lot of praise and a treat.
Lady does not do rain. If I'd take her out too soon after it stopped raining and a drop fell off the trees on her, she'd would just sit down and refuse to move.
