I've been using fletch tape, but want to try some DUCO. The stuff  I have seems to thick to apply well.

If your Duco is too thick, its too cold. put the tube in your shirt pocket for ten to fifteen minuites and it will be thin enough.
Bob

and if that doesn't do it, you can put it in an applicator bottle and add a few drops of laquer thinner.... I like it a lot thinner than it usually comes in the tube.  

I recommend an aplicator bottle as well. The nozzle on the tube is too big to make a neat glue line. A pin hole in and applicator bottle works just right.