Stories from whose who know rules and especially practices are most welcomed.
My present advice is that you either have everything properly documented or else just keep low profile and hope that unmotivated inspectors will leave you alone. An attempt by a client to declare a camera resulted in a disaster. (A disaster happily sorted out, and I hope he made it part of the story – see Examples of Jobs and Services.) Later same fellow and several other travellers in a very similar situation just pretended nothing was happening, and nothing did. Cultivate a tired FO look, and your chances of getting in troubles drop way down not just during the border crossing.