It worked best for me by opening the Viv often and moving stuff around and changing his water. Picking things up and putting them down, just being there and doing stuff without touching him, and when it's feeding time use food to lure him into your lap or arms and then stroke and handle whilst feeding to get him used to human interaction. now I can open the Viv at anytime with or without food and put my hands/arms in and so whatever I want including pick him up without a problem.
Gauging when he has ha enough is the key and every Bosc is going to be different. The bath technique did not work at all for me my Bosc hates the bath and either goes mental and stresses out or plays dead