Vaseline is not your best wood treatment. Better would be mineral oil or better yet, a good wax.
DON'T treat the inside of the bowl with anything! Your best bet is to line the bowl. Figure out your bowl size first...use pipe. (Best is old ammunition cartridges....45 is a great hash size, .50 is great. Drill out the primer and you already have a shelf for your screen. Use a small drill first, for your smoke path. Then enlarge the hole to the size of your brass sleeve. Which you can cut down to size. This is an excellent bowl.
It's hard to drill a long stem, so sometime's it's better to make the bowl out of one piece of wood or bone (try pipestone or soapstone--carve easily, polish nice , look great, and smoke cool!) Then drill to insert a stem. Stem can be a bone shaft available from beading stores or a piece of copper pipe you can then wrap with leather or some such.
Have fun.