If you actually need to write…
For individual Kanji, I find the best way to be following RTK series, after you have known a decent Kun and On readings, and a repertoire of vocab. What I really do is Basics from RTK and practicing Kangxi radicals… and then practicing writing by WaniKani levels’ order.
I find Leebo-introduced Iverson method, Printout for kanji study/writing practice using the Iversen Method, to be a big help too. I think it relies on shadowing and a good visual memory.
If you are OK with Anki, using AnkiDroid (Anki on Android) allows you to write a very big Kanji, like 15x15 cm, so it could be a big help to writing properly. There is a deck for WaniKani kanji here – [Version 1.05 | 2016-01-31] Anki deck for kanji writing practice.
Writing individual kanji does help remember Kun and On readings, and compound words, so it isn’t really a waste of time…
For Kanji in compounds and actual sentences, a better way is probably get a real Kanji workbook for Japanese children and Kodansha Kanji Learner’s Dictionary, which helps differentiate usage between similar Kanji.
Skritter, which is online, might works as well. I don’t know if it can be done offline.