I don’t think soaking in Dawn removes mineral scale. Maybe if the water in your Dawn soak is distilled, you will get less mineral buildup? This is why I settled on daily boiling in distilled water, skipping the Dawn soak and the vinegar soak. Because I boil every day I don’t fear tenacious biofilms; if I did (it’s not an unreasonable concern) I would soak in Dawn also. Everyone settles on the trade-offs they can live with, and this is mine.

I soak mine in dawn and rinse immediately after each use, and boil in distilled water 1/week. I also disinfect daily 1/day since I use the aerobika flutter device/neb parts in the morning and an additional nebulizer (without the flutter device) in evening. After nebulizing in the evening, I throw both am and pm parts into the microwaveable bag and microwave for 3 minutes. Maybe overkill but it's fairly easy.

I never didn't think about the mineral build up, I will add soaking in 6% acid vinegar 1/month.