Direction follower ?

Hi all,

I am still toying with cutting glass and found that a weighted
standard glass cutter will cut glass easily enough.

the problem is turning the cutter so it is always facing the
direction of cut. This is similar to knife cutting vynal, but it
appears to me that the action would have to be pretty accurate in
angling in the direction of cut so as to score the glass cleanly.

Any ideas on how best to do this ?

Dave