OK i will try to even things out,
I did use a perspex cover on the first couple of locks i tried with the CB's, it does allow you to see how the tool works. Once i knew how the pick works i ditched using the perspex when i moved on to learning other locks.
It is the 'feel' that you have to learn, and with the perspex no matter how hard you try you cant help but look and i found it took me longer to get the 'feel ' that way so now i dont use it.
It may take you longer to get a new lock open but the time you spend trying is far more valuable in the long run because you now have a feel for that type of lock.
I also think its important to note that once you have picked a new lock, change the leavers and do it again. Every time i get some new stock in the locks dont go onto the van until ive picked them atleast once,(unless i need them for a job) that way you can become familier with different lever combinations etc.
(please dont tell my customers)
sorry but i have to dissagree. 
if you are first learning then a perspex cover will help you understand what you are feeling. dont consertate on the visual but use it to comfirm what you think you are feeling 
