Essentially what Buffett suggests in the article is a cap and trade system on imports.
To import $X worth of goods the importer must have $X worth of ICs (import certificates), which consumes those ICs. ICs are created when exporters export, with each dollar of exports creating a dollars worth of ICs.
ICs are tradable so an exporter does not have to use the ICs created by their own exports. They can sell them to importers.
Note that under this system it is perfectly fine to have a trade deficit with any given country, as long as their are trade surpluses with other countries that balance it.
Trump wants trade with each country to be balanced (or a surplus).
Consider this hypothetical.
• Country A needs to import some natural resource. They import it from country B and use it to manufacture something.
• Country B doesn't need anything that A makes, but does need something from country C.
• Country C doesn't need anything from B, but imports the thing A is manufacturing.
If Trump were running country A he would view this as A getting ripped off by B. Under Trump logic B would be getting ripped off by C, and C would be getting ripped off by A, but he wouldn't care about the former and would probably by bragging about the later but not calling it a rip off.
One of the big reasons money was developed in the first place was so goods did not need to be balanced between each pair of traders.
Before money if a farmer had chickens and wanted a goat he had to find someone who wanted chickens and would trade a goat for it. If the only guy with goats he could find didn't want chickens but wanted a pig the farmer was out of luck, unless he could find someone who had a pig and wanted chickens. It can keep going...maybe pig guy wants a cow so now the guy with chickens also needs to find someone who will trade a cow for pigs.
Money made it so trades become money for goods instead of goods for goods. Chicken guy just needed to find someone with a goat for sale for money instead of finding someone with a goat who specifically needed chickens.
Same thing applies to trade between countries, and for some inexplicable reason Trump wants it to work like the old chickens for goat days.