I had another attempt at this today. I should mention that I am doing WBTB stuff for DILDs in the morning and then attempting WILDs after a full 8 hours sleep so I am making it more difficult for myself.
Anyway, I followed your advise and it did help. What came to mind was that I had been controlling my breathing up to the point where the heavy breathing starts, but surely your subconscious needs to take total control over your breathing as you enter a dream, so I think the laboured or heavy feeling is because your waking and subconscious minds are both wanting to do the job of breathing for you. Anyway, I just stopped thinking about my breathing and thought about the sensation of air passing through my nose instead.
With this frame of mind it wasn't uncomfortable at all. I had loads of various sensations and floating feelings but a total absence of any imagery. This may be because I had already had a full nights sleep.
I know you can do this any time of day, but while I am learning do you think I will have to give up my DILD work and use my WBTB for WILDS until I get them working, or is it realistic for me to go for the WILDS during the day straight away?