i also dont take gymnastics, but i taught myself to do a bridge in this way: i stood next to something a little lower than shoulder height and put one hand on it (i used a dresser, but other things are fine). then with the rest of my body, i slowly went down into a bridge, sliding my hand down the dresser until i got down into the suitable postition, then added that hand as well. this way may not work for you, but it did for me. after about 10-15 times of doing it that way, i could go back down into one without the dresser. you may want to put pillows underneath you until you get more confident! also, make sure you dont continue if you hesitate. you'll hurt your-self alot easier! going down a wall is fine, but that also means you're putting all of your trust in another object instead of yourself. i used to do it that way.
by the way, i find it easier if i stretch out before hand-- put your hands on the back of your knees, then lean back as far as you can without toppling over; like you were doing a bridge without your hands.