Hey buddy, I am glad to see that you have an open mind. Your skills are not why you had bad results IMO. Trust me, some Auto strains just don't like the high stress training. I remember when people freaked out about topping Autos. Most Autos take topping ok. But mainlining is much more aggressive and stressful. You could be the best grower around, and it would not matter. Once many Autos are stressed too much, they shut down normal growth, take forever to flower, or yield poorly. A general rule of thumb is that most highly Indica strains don't do well with too much pruining. For example a 24 Carat or Sour Crack are highly Indica. They finish so fast that they prefer less stressful conditions. leaf tucking and minor LST is about the most you want to do on most true Indica strains. You would probably have better luck using a large aggressive growing
Hybrid. So Strawberry Nuggets is not a great choice, as it is Indica based and BOG background as well. I personally like to grow Autos with minimal training the first time I grow an Auto strain. This tells you what the plant does on its own. Then you know the natural structure in your personal garden. I will do light pruining, leaf tucking, and light LST. But I personally avoid topping the first time I grow a strain. Just keep the main Cola decently level. Then you have a baseline idea of what it looks like, how fast it finishes, and what it yields normally.
Sometimes training can extend the total grow time by exposing more future budsites. Mainlining is a great technique for some strains. But for some strains, it can literally shut the plant down. It might not flower correctly. And that is not your intension, but it can happen and you can't reverse the effects. If you really like to mainline plants, just be fully aware of the plants genetics. The problem with Autos vs Photo is that each plant is different and you can't clone Autos like Photos. If you find a Photo pheno that mainlines well, you can clone it and keep it. It is Very hard to replicate Auto grows, unless it is a refined strain. Good luck brother, I will be following. Peace slowandeasy