2 questions about a side gig

Hello, I have a main employer job with a yearly W2. I also have a side gig with a YouTube channel.

 

1st question - to avoid paying quarterly taxes for my side gig, can I just withhold additional taxes with my main employer biweekly?

 

2nd question - if my side gig is YouTube, what exactly can I claim? Example - if I flim and post a how to DIY plan/build a deck video, can I claim all tools/materials used for this video?

 

Thank you!