Here's a list of links to articles that talk about what makes a good slide, then links to a great little lesson (or two) from a fellow who really understands the 'slide technique'- and demonstrates it nicely for beginners- and finally a search link for 'Guitar Slide Interest Groups' on Facebook. Joining a group or two can help you quickly get your balance, with advice and recommendations from other folks who've walked the same path you're on.
Note- the practice part is entirely up to you.
A bit of good advice on slide selection:
Article in Guitar World - by William Baeck - How A Slide Taught Me To Make Up My Mind
Scott Ainslee, Teaching Artist and Performer - On Choosing a Slide For Slide guitar
A couple of terrific starter lessons for beginners:
Matt Smith Killer Slide Lesson #1
Matt Smith Killer Slide Lesson #2
and if you liked his first two lessons, here's a link to all eight Matt Smith Slide Lessons:
And this is a search link for Facebook Guitar Slide Interest Groups.
And please, let us know if we can help you with a custom boro slide! In color! Creativity rules...