Use multi language dictionary with aspell

I have a large .tex file that contains two languages and I want to spellcheck it without going crazy. So just spellchecking for one language and pressing "ignore" for words from the other language is not an option. So I read up on aspell and found out you can define your own .multi files to combine dictionaries. But apparently you can't do this for dictionaries from different languages, it throws an error (or, if you're working from a GUI, the dictionary will just appear empty). Also, I found a bug report putting this feature on the wishlist, but it seems no one has implemented it yet. So, my question is: Are there any sane ways of using two dictionaries for two different languages at once? This problem gave me a headache and there's next to no documentation on how to do it on the internet. So, I'll put up the workaround I found as an answer, to save anyone else (including future me) the trouble. But if you have a better solution, please post it.