Finishing ... the other half of making a cue.
I think you are referring to Poly Urethane and if so General finishes makes a good one.
Best to spray it on but there you need more equipment and the space for it.
Brushing it on is tricky at best and rubbing it on with a rag gives thin coats.
If you get it on thick enough to look slightly milky the cue needs to rotate while it sets up
or you get runs.
If you have a well ventilated work area you might try a super glue finish.
Use thin and give it several coats before sanding it smooth.
Super Glue can produce a very nice finish if done right.
Willee