Hmm I don't know if you can make them thicker - not having used PSE.
I think probbaly your best best is using a brush since you heave more flexibility with that.
I just wrote a series on this for the tutorials area but since its still not fixed yet here are the direct links to download the tutorial.
I think Part 1 will be the most help for you.
http://www.sbbelements.com/team/tuto...ungeedgeP1.pdf
http://www.sbbelements.com/team/tuto...ungeedgeP2.pdf
http://www.sbbelements.com/team/tuto...ungeedgeP3.pdf
http://www.sbbelements.com/team/tuto...ungeedgeP4.pdf
I hope these help
