The shots don't look bad for 35mm. I'm assuming you are unhappy with the visible grain. Tips on reducing visible grain: 1. Different chemistry yields different results; I find the Tetnal press kit produces more visible grain in my scans than the Rollei Chemistry. 2. For Portra 400 I err on the side of overexposure; negative film can handle it well and it will help reduce visible grain. 3. Scan at 2000 to 3000 dpi with no sharpening, apply your post processing changes before reducing the size, reduce size then sharpen to taste remembering that sharpening will enhance the visible grain so its a balance of what is acceptable to you.
Hope this comment doesn't stray to far into digi-land for APUG or I will be chastised........... Another thing I have read you may want to consider when evaluating your shots is that blue will typically have more noise than the other channels in a negative scan. This is because that channel would have higher amplification relative to the other channels in a negative scan to compensate for the orange mask. This is consistent with what I have seen and makes sense. So perhaps overexposing when you have a lot of blue in the frame may help to reduce apparent grain in your scans. I have not actually done any purposeful testing to verify but it makes sense because it would result in a higher SN ratio on the blue channel. Good luck!