I am currently using a nipple shield and starting to wean my daughter off of it. She's now 7 weeks. I've been using it since day 5. Here's what I do:
Nurse with the shield for 15 minutes (this draws my nipples out and by this time, my baby has the sucking motion down good) then slip it off and put her back on me. Sounds simple, right. It is. I was so scared to do this that I didn't start trying until last week. I thought to myself, "what if she won't latch on again without the shield?" then I thought she might need to be supplemented with formula for that feeding because she'll get too frustrated to latch on properly (which has happened in the past)... well, start her on the shield for maybe 30 minutes, then pull it off (by then, she already has gotten most of the fore milk and hind milk anyhow)and it's more for "practice and comfort". If she doesn't latch back on, that's okay because she got all the nutrients in the milk with the shield. IF you do have a SUCCESSFUL feeding without the shield, the next time, try to shorten the amount of time of her on the shield, pull it off, then put her back on. (I did this starting from 30 min on the shield the first time, then 25 minutes on the shield then 20 and so on..) I can't say it works all the time, but it's getting there. I've been trying to wean her off for only 1 week now...
Believe me, I understand how you feel. I felt envious of other mothers who just lift up their shirt and nurse, whereas I have to run to the bathroom, put on the shield and my biggest fear: what if the shield drops on the floor, especially if I'm not at home... Needless to say, I bought 6 nipple shields! Anyhow, all I can say is, "just try it" and don't be afraid of your baby not latching on correctly the first time. The feeling of her nursing naturally without the shield was amazing!!!
Good luck and feel free to email me with any Qs, as I am going through the "weaning off" process at this moment as well. =0