Not much point training until dd2 can tell you before she wees that she needs to, and can hold on until you can get her on the potty. However, her telling you that she knows she is weeing is a good sign that she has growing awareness of her bodily functions.
You could put her on the potty at each nappy change to get her used to the idea, you can still use nappies between times. You could also have nappy free time with a potty close by, and see whether she sits herself on it before she wees. This would be a good indicator of whether she knows she needs to wee, and that she does it in the right place because she could hold on long enough to get on the potty.
I'm a "they'll do it when they're ready" kind of person but my DS2 (21 months) started to pull at his nappy and say "poo" or "wee" this morning so I took his nappy off, told him where the potty was and what is was for and he has used it all today and not had any accidents. Loads of praise for using it or just sitting on it and putting the poo in the loo is a bit of a theatrical experience
It may not last, that's fine too, at least he gets used to the concept of it and what it is for.
Yep. I am also a when they say they ready person. My dd started taking nappy off at each wee and likes to be naked, (thats another story). So I bought her some knickers and also made potty available and that was it, she was off. She was 25 months and have wondered if it would have worked sooner, but luckily it's been so easy am not stressing about it. DS was 3 years but we waited till then as moved house etc etc. And I do think boys are less able to concentrate and get distracted. Go for it and see. If not wait a bit and try again later.