Thank you so much for your advices.
I finally contacted local dealers for GC and Jensen and both dealers said they would give my DT a chance to try their staining systems.
From what I've heard, GC Lustre has gained good reputation among the users already, and Insync is about to be imported now.
My DT will choose his best between them after trials.
Anyway, thank you so much for your words, they helped me a lot.