I discovered these recently and tried them out with reasonable results.
I bought some exchange 1mm tips (the standard is 2mm). For 1/300 scale figures I think 0.5mm tip will be needed for crossbelts and other detail, but I had some success using the 1mm tips on 1/100 models. The advantage is that the tip is rigid. The pens work best on raised detail, and will not go well into recesses.
I will persevere.