A neat example of the failings of heuristics when applied to mazes is the hedge maze at Egeskov Castle, Denmark (aerial photo, 2D diagram). It's constructed such that if you choose paths seemingly pointing towards the goal, you'll get caught in an infinite loop - and in fact, the most effective route can be found through a heuristic of choosing the path seemingly pointing away from the goal.

How long did it take to build this skill, and how did you do it?

I quite like Dictionary of Numbers. It provides comparisons for e.g. lengths and amounts of money. Example: I found $200 on the street --> I found $200 [ ≈ Low-end bicycle] on the street.

Danish: møbel (2), stol (1), lænestol (3)

Furniture is countable in Danish, so the word I wrote means "piece of furniture".

It's actually really weird that furniture is uncountable in English. Most other uncountable nouns make sense - you can't really count how many milks you have. I wonder how it came to be that something so tangible is uncountable in English?

I find that making up mnemonics works well to combat interference. They don't have to be good mnemonics for this to work.

Example: I noticed I kept mixing up the Spanish words aquí (here) and allí (there). I then made up the mnemonic that aquí has a "k" sound so it's close, and allí contains l's so it's long away. A few days later, I encounter the word "allí". My thinking then goes "That's either here or there, I keep confusing those" -> "oh yeah, I made up a mnemonic" -> "allí means there".

I wonder how well this method would work for others.

I speak two languages fluently. I observe that it is slightly easier to count in one language and read in the other. The full ranking is reading without counting > reading English, counting Danish > reading Danish, counting English > reading Danish, counting Danish > reading English, counting English. That counting Danish > counting English is presumably because I don't count in English nearly as often. I used an LW article as my English text, and a physics textbook as my Danish one. I would say these two texts have similar difficulty.

Like bramflakes, I was surprised by how difficult it was to count while reading in a different accent.

These comments really highlight how different people need different surface tricks - to me, the distinction between Working Really Hard and Moving Towards The Goal makes a lot of sense, and you helped me recognize that I sometimes use the former mindset when I know from experience that the latter is much more effective for me. I will now make an effort to change that habit.