Some of the letters from higarana and katakana are the same or very similar which helps. (へ and ヘ) for example (や and ヤ), (か and カ) and so on, I agree that katakana is harder but I would recommend just using focus review a lot as well.
Writing practice is surely a good way to memorize characters as always but it's common knowledge already.
So, other than that, I recommend reading and reading katakana words as practice. Borrowed words in Japanese are written in katakana. Sometimes it is hard to recognize the word even if you can read and KNOW the word. Since it is adapted to Japanese pronunciation, the word has small modifications making it hard to recognize more than you think.
This way you can practice your recognition of katakana characters and the words as well.
The most important thing is to imagine something behind it. Your brain will remember it base on your imagination much better. Better made up stuff, faster learning.
Try physically writing them as you practice and also try to write them from memory to test your knowledge. You can also look up an older post on these forums, where people gave some mnemonics to help differentiate between シ,ツ,ソ, andン
