Personally, I've never had to place the 'commissions open' title in my profile, but I do have a lot of friends that do this and it does help them to get commissions. I'll be honest, I've been doing commissions via twitter for a while now so a lot of my customers are either referred to me by a past customer I've worked with or they are a repeat customer. I usually create and pin a post on Twitter from time to time and it usually gets liked and retweeted. Sometimes people even share the post with their friends/family who might be looking for someone to commission art from. I also participate in a lot of art discussions and webcomic/art hashtag events on twitter as often as I can.
I don't have a huge following either (I have a little less than 830 followers) but my commissions are somewhat niche based. I used to advertise my services on my Twitch channel (I used to do stream art stuff a lot) and the amount of foot traffic I got to my website was overwhelming to say the least, so I think my past Twitch history as helped a lot. I do mostly character designs, Twitch emotes, panels, loading screen designs and sub badges, so usually people I've made emotes for, for example, will send other Twitch streamers my way via twitter. I hope that makes sense.