What's the grammar structure for "かな"?

Question

How should I use this "particle" with nouns, な adjectives, い adjectives and verbs? In a web I saw something like this:

For nouns just add "かな" after the noun. For な adjectives you must put の and, if you want, な, between the adjective and "かな" (but in the examples all of them were with なの). For い adjectives just add "かな". For verbs you can add の between the verb and "かな", but it's optional.

These instructions don't sound so trustworthy. What's the real way to conjugate that words before "かな"?

Answer 1

For nouns just add "かな" after the noun.

Correct, but it is also correct to add 「なの」 between the noun and 「かな」. Adding it would help draw more attention to the question from the listener (because it makes the speaker sound like he is more interested in his own question than when he does not add 「なの」).

For な adjectives you must put の and, if you want, な, between the adjective and "かな" (but in the examples all of them were with なの).

Makes no sense. You cannot say 「きれいのかな」 or 「きれいのなかな」.

You must say 「きれいかな」 or 「きれいなのかな」.

Note: 「きれい（な）」 is a na-adjective. In my own experience, some learners seem to let that 「い」 fool them into thinking it is an i-adjective.

For い adjectives just add "かな".

Correct and it is also correct to add 「の」 betwee the i-adjective and 「かな」.

You can say both 「あついかな」 and 「あついのかな」. The 「の」 has the same effect as 「なの」 does, which I have discussed above.

For verbs you can add の between the verb and "かな", but it's optional.

Correct.

You can say both 「来{く}るかな」 and 「来るのかな」. Again, the same の/なの effect.