Allow your dog to work through an issue actively versus by hiding/blocking the problem.
Do you cover with your foot a piece of food on the ground to work on "leave it"? Do you physically block your dog from seeing a dog it wants to react towards? Do you hide your training aid (ie. treats or clicker) behind your back?
By doing this, you are 1) highlighting to your dog that there is an issue, possibly making your dog even more suspicious, you are 2) telling your dog "you can't handle this successfully, so I need to cover things up for you" (an implied mistrust that your dog can make the correct choice), and you are 3) not offering a normal, organic posture which you would/should have in a real scenario.
You are in charge of setting your dog up for success. You always have a leash as a tool. Allow your dog the chance to process what's in front of it and show them the right (and only) way by using your training aids and equipment (leash, collar, treats, etc)
If you cannot work on a behavior without your dog bumping into the clicker or treats, work on that impulse control first before you work on what you intended to work in. If your dog continues to be stupid lunging into the collar to get to another dog, move further away. If your dog wants to take what's on the ground, plain and simple don't let them via leash/impulse control and their correct choice to disengage from what's on the ground.
In training a behavior effectively and proficiently, we often need to teach intermediary, supplemental steps or behaviors to be able to train the intended behavior. Sometimes, we need to take it way back to a basic skill set to prepare our dogs to handle the intended lesson.
In closing, I will always say that if the above works for you, RUN WITH IT. No questions asked. If you don't get proper progression, however, or your dog fails in a real scenario repeatedly, be open to consider a different approach.