Not sure what others do about training with holding blinds but we never train without setting one or two up. I guess the drill is to desensitize the dog to the holding blind which blocks the view of the noise and activity that is going on around them at a trial or test. I start in the front yard. The holding blind is set up and M is walked in behind it and given a good sit, nick, sit and then I leave her in the blind and walk away. If she moves out of the blind then the process of walk into the blind, sit nick, sit is repeated. It does not take long to get a reliable sit in the blind. Once this is proofed the next step is to leave M in the blind, walk away and fire the gun. Again if she leaves the blind the sit, nick, sit correction is given.
M is now stable in the blind with gun fire so we move on to fire the gun and throw birds (bumpers) all around the blind, from in front to hit the blind, over the top so they land behind the dog, to both sides of the blind to land where she can see them. M is not allowed to move out of the blind while all this is going on, if she does then the correction is given. Once this is stable the next step is to set up two blinds and have a working dog. M stays in her blind while another dog works, usually a short double. Again she must not leave the blind while this is happening.
Another thing we do to make sure the dog understands she must stay in the blind until you give the command to leave is we put two dogs in the same blind, the dog may not leave the blind until she hears her name called. Again correction for not obeying the stay in the blind rule.

Not sure if this kind of training would help RD but she is much like M and Elle in drive so making the holding blind a place to sit and stay rather than an obstacle blocking her view might desensitize her.