Riding with a bitless bridle should require very little change to the aids used when riding with a bit. Most horses take straight to the bitless bridle without any retraining. We have converted all of our trekking, lesson and own horses to bitless bridles with no problems or retraining issues, from youngsters being started bitless to 20 years 'old timers'. There may be exceptions to this rule of course, and I would recommend trying your horse bitless for the first time in an enclosed space.
If you leave your horse with his bridle on waiting for any reason, it is a good idea to loosen the noseband a hole to allow him to yawn and relax. If you allow your horse to eat whilst bridled, again loosen the noseband so he can open his mouth properly. It is easier for the horse to snack on grass etc. without a bit in his mouth, but with the noseband done up this can lead to chafing under the jowl.
Please do not tie your horse using the bridle. If they spook/pull back it is likely the bridle will break as it is not designed to take this kind of strain. If you leave your horse standing bridled, use a headcollar over the top of the bridle.
If you have any problems or queries please contact me.