Hi Fiona!

How are you?

In Russia you can't work officially without a working visa (note: business visa also doesn't permit you to work) or a residence permit! You can however work unofficially and it's pretty easy to find such jobs but you can't really do that until you get there. Being a native English speaker you'll probably find it easy to find students to tutor privately! There's thousands doing it and it's not that difficult to get into and you can expect to earn about 1000rub per hour (90 minutes usually) in big cities(Moscow and Piter).

If you have a british passport I'd recommend doing it with that especially since you are living in Ireland. Are you in the Republic of Ireland or Northern Ireland? Basically you do it all online and just need to send your passport and documents (if you don't have documents for a visa, you can easily get them online for tourist visas up to a max of 30 days or a business visa for 90 days max). You can either send the documents and have your passport returned by mail or if you go to mainland UK you can go in person to collect your documents either at the visa processing centre in Edinburgh Scotland or in London.