The main thing is to show that you are working abroad during the period for which you want to pay Class 2. There are some other conditions, and I am not sure if 'abroad' covers all countries, but the best thing is to make your best case and see what happens.
In my case, I got a record of my PRSI contributions for Ireland and sent them that. I also sent a list of all my employment history since leaving the UK and I backed this up with letters of offer, employment contracts, and a recent payslip to show I am still with my current company.
To be honest, I think I went a bit over the top, just because I have reasonably good records. I would say that the PRSI record was the most important one.