DD (19mo) gets her potty when she wants to do a poo-sometimes, not always-and will sit on it, while still in her nappy and dressed. This suggests she's understanding what it's for and that she's about to poo I think? She's also started clutching herself occasionally and I'm pretty sure that's linked to when she's weeing. However, she's not talking (or barely)-would it be best to wait to potty train until she can articulate it?
Why not just put her on when she asks a- rather than full blown potty training. Maybe go to pull up pants (potential for easier "down and up"). If that works well (consistently asking and dry pull ups), then try proper pants. She sounds brilliant: you probably want to allow her to progress in the right direction without putting too much pressure or stress on either of you.
Yes, that's a good idea...at the moment I don't think she's very consistent with it but pull-ups plus potty when asked for might encourage her. She goes to nursery 4 days a week and sees other children using potties so she may in part just be copying them.