If you're training alone with wingers I think you have to plan out your marks very well. Often with hunt testers they make the line to the bird easy and the bird hard to recover due to it landing in brush or heavy cover, odd spot of terrain etc. I would ask you to consider making the line to the mark more challenging but having the bird land in a relatively easy to find spot of land. If needed seed the AOF with 3 or 4 bumpers/birds. This way if you do have to handle it most likely going to be for fighting factors to hold the lines and not because the dog can't find the bird and needs handled in the AOF. As well if the bird is easier to find you building confidence to finding the bird where they saw it land and then when you have gunner help make it tougher so if they get there and can't find it, gunner help can help build perseverance.