Apologies if there is already something like this and I'm just being blind! But on 2+2 there's a sweat session thread where people post if there interested in sweating/being sweated.
Might be an idea for the learning to win/nl section. People just post their limits, game type, and what they are looking for. Example:
'Playing NL10sh @ PS. Looking for someone playing NL10/25+ for a sweat. Also willing to sweat anyone playing NL10 and lower pm if interested'
(obv this could be for plo/sng etc...)