Blood sacrafice to the gods (/j)
Real answer: It's never going to be regular or consistent until you've reached a loooooot of followers on multiple platforms, or,
get lucky. I got my first commisison before I even offically opened comms, and then not again for months. When I opened comms, I got maybe one or two and then dead for months.
It's about luck of the draw, but there are ways to push the luck in your favour. As
@Sonachine69 said, Twitter can be bad if your personal twitter and art twitter are one in the same. Clients want a quick look through your body of work with as little effort as possible, if you're serious about getting commissions on twitter (and it
is a viable platform, 90% of my commissions come from Twitter) you
gotta have a clean media tab. I'd even go so far as to rarely ever use your art twitter for making posts about personal or fandom stuff. I like using my art Twitter to engage with my audience who like my art, and to engage with other artists. (another tip, be nice to people online, compliment their art if you like it! Don't be a kiss-ass, but what goes around comes around. If you support your fellow artists, big and small, they may support you back)
As for other social media platforms, it never hurts to spread yourself out there a bit. It can be a lot of work, but once you get a system going, it's a lot easier to post your work everywhere at once. Whenever I post a new piece of art, I have 8 different places I post. And that's a lot! But that's just the cost of business sometimes.
I have also noticed that whenever I post about commissions, I'm more likely to receieve them, so one post that you pin might not get the eyes you need! Quote-tweet it or make another one, someday someone will take the bait and you'll get that ball rolling.
I'm happy to answer any questions, queries, concerns you may have, and I wish you luck on your journey!