My DW taught both of our girls to go by saying "Time to go Potty". They are now 10 and 7 and they still tend to go faster when you use the words. Penny (DW) also used small treats as a reward when the went "Potty".
We have a Fenced in Backyard and during daylight hours they are free to run around but at night I take them out in front on their leashes. We have a lot of Wildlife around here and the lighting in Front is much better than the back, plus I have better control of them. It is a habit now and they know which door to go to depending on the time of day.
Our Little Sandi will go #2 just about every time we go out but Macy will only go at certain times.
As for training Doxies, my Family has always had them and I would love to have one but after keeping my Mom's Trouble (a 13 year old Mini Dapple) I found out having to German Females in the same house did not work out very well. LOL
Anyway, Doxies are great at training, just give it time and THEY will train you.