In a similar situation here - I was just feeling very chuffed with myself for keeping the pot of touch up paint that came new with my 1996 Kona Explosif.. only to open it to find it was solid . To be fair my beloved bike needs more than a touch anyway and 5 ml was never going to cut it . Don't tell any purists, but as an interim I just used some matt black metal paint on the chainstays.. not in any way original or professional, but looks better than the chain sucked and bashed-up tubing that was on show before!!