I’d say, start with getting over the fear of looking up Kanji you don’t know the reading. The fastest way over that is probably handwriting all of Kanji in RTK. Alternatively, learn Kangxi radicals and variants. Then, looking up in a smartphone dictionary can be done with handwriting. And indeed, another requirement is allowing yourself to use a dictionary more.
A slower way is to learn at least one of the readings of each Kanji, maybe via vocabularies, like what WaniKani is doing. But then WaniKani not only not having some Kanji, but also missing some useful Kanji readings. In the grand scheme of things, for most Kanji, at least one On’yomi is required to be known.
Learn phonetic-semantic compositions and the guess would be better. Wiktionary.org might be a useful inter-lingual resource.
Keep reading and continue to lookup, until you feel that you don’t have enough time to lookup, as well as you have a good enough guess. Even then, there will be many vocabularies that are good to know in advance.
For just prepping vocabularies, but perhaps not really directly Kanji, manga-kotoba, jpdb or koohi.cafe can be helpful.