For us, we can manage the "No foreigners can own erb" "No erb can be created or destroyed" stuff rather easily. For a country we have dual citizens (eg Gralus, which I know is not a country anymore but its a good enough description for CITRA participants), they can step up and do market exchange. So if a Gralan like Demon of Fides wanted to buy an image off Scott for 70 erb, he'd go up to a dual cit like me and say, "I'd like to buy an image from Scott for 70 erb. I'll pay you 80 CITRA points for it."
And I'd say, "100 and you have a deal." And then I'd pay 70 erb to Scott from my account (so no erb ever leaves Shireroth or touches foreigners hands) and Fides would pay me 100 CITRA points back in Gralus. Scott would do the image and give it to Fides and everyone would be happy.
If the opposite occurred - say a Shirithian like Jonas wanted to buy a Gralan Insult off Nicholas the Mad, which costed 40 CITRA points, he might say to me, "Andreas, can you sell me 40 CITRA points? I'll give you 30 erb," and I'd say "No, 40," and he'd say, "But I'm your Duke," and I'd go, "Fine, 35." And he'd pay me 35 erb, and I'd pay Nicholas 40 CITRA points, and Jonas would get his copyrighted insult. And I'd make a nice margin on the whole deal. Simple enough?
Where there isn't a dual cit, or they aren't rich enough to exchange (say an Ocian wanted to buy access to an EBR broadcast), then the Shirithian government can step in. They can pay erb to Jess and the Ocian pays the Shirithian Government several thousand Tolars. The government then has those Tolars available when a Shirithian wants to purchase an Ocian good.
The one problem is if a Shirithian wants to buy something from a nation we don't have dual cits with and haven't already got that much money ... but in that case we can probably do a deal with extending erb credit to the nation that can draw on the government account. That way they don't own erb and extra ones aren't created, but they have it easier the next time to get some erb, because the government always has plenty.
So there's currency exchange sorted. The second equally crucial aspect is we'd need several entrepeneurs to set up advertising companies. Shirithian companies could register with them, and then the add companies go to other nations and post a list of all the registered Shirithian companies' goods and services we can offer. Because, lets face it, currency exchange is all well and good but 90% of micronationalists won't bother trying to sift through our MiniTrade forum on the off chance they find a service they want. We have to advertise it in other nations' business forums. This both encourages our citizens going abroad and getting to know other nations a bit (great for tieing with diplomacy) and also helps our economy do better because more people are purchasing stuff.
My ramblings make sense, yes?