i use them alot too- the way prism99 explained- i (assume) there is a learning curve & all new techniques take a little practice- i have found the really wide ones seem to be a little more difficult than the narrower ones- i did have some trouble with the 1" the first time i used it- but i just re-starched & increased the length of my starting point (pulled about 3" out & adjusted the folds- then pinned across with a large safety pin- to help guide the strip...the 1/2", 1/4" & 1/8" ones are so much easier than the wider (in my opinion) i've been using them for so long i don't remember if it took a long time to figure it out- i do remember seeing a demonstration once though that was kind of an (ah-ha) moment. Since i tend to do alot of stained glass applique i found it very cost effective to make my own.
starch, only pull out a couple inches at a time & press until you get the hang of it...after some time you will learn it's a great time saving tool. (i think for 1" or wider i would not bother with the tool though- they are much better for narrower bias strips)