As some of you may already know my wife started shaving with a DE on Tuesday. The only complaint she had so far was not knowing if the razor is working or not during a pass. I decided to use the Weishi this morning with an Astra SP. First off it is definitely milder than my 23c and you have to pay attention to the "sweet spot" in the angle you hold it at. It is definitely more sensitive to this than my Merkur. In saying this I got a great shave albeit with 4 passes and a few touch ups, but my face is happy with minor irritation is a few small areas. Probably due to the number of required passes more than anything. Now that I have used it I may be able to be more helpful when asked for advice from the better half on her next attempt.
Tell her, practice, practice, practice. Memorizing a razor's angle can take time. Hope she has fun with it! My wife loves her vintage fat handle tech.
Since you have used her Weishi you might let her use the 23C to see if her shave changes. If so, you might need to search for a more aggressive razor for her or let her have the 23C when you get the 39C.
Angle comes with time but each razor is a bit different. If she settles on one very soon she will wonder how she could not find it. Hence the 30 day rule.
