He is very articulate but he doesn't seem to be a visual learner.
Spelling is not a visual skill. The basic skill needed for spelling is the ability to identify the individual 'sounds' which make up the spoken word and to write the letter or letters which represent those sounds, in the order in which they come in the word. This method is entirely logical as this is how written 'words' were originallly developed; by assigning a symbol to each 'sound' and writing those symbols in the order in which the sounds occurred in the word.
Unfortunately, because English is a mixture of words from many different languages which in many cases retain the sound/symbol correspondences of the originating language (which differ from language to language) English does not have a simple sound/symbol corrrespondence system. This complicates learning to spell but it is not impossible. Also unfortunately, many teachers do not understand this simple principle and try to teach spellings by expecting children to memorise the letters in a word and the order in which they are written. This method does nothing to help children understand the logic of spelling and favours only children with excellent memories.
I'm afraid that computer programmes are not particularly helpful for improving spelling as they rely on visual memory and do not emphasise the relationship between discrete sounds in words and the way that each is 'spelled'. Additionally, good spelling involves the use of kinaesthetic memory as every word has a unique 'feel' to it when written. Picking out letters on a computer keyboard does nothing to develop kinaesthetic memory of the hand written word and is of little benefit unless the child is only ever going to type everything they write (as clearly it will eventually develop kinaesthetic memory of typed words).
Look, Say, cover, Write & Check is not a good way to 'learn' spellings, particularly if letter names are used instead of sounds. I would suggest initially concentrating on getting your son to break words into their component sounds and then try to spell each sound in order. Start with words containing simple letter/sound correspondences so that he really gets the idea of the logic. If he can already do this you could use a modified version of Look, Say etc.
Say the word and identify the sounds in it
Look at the word to see how each of the sounds is spelled (there's usually only one unusual sound spelling in a word so concentrate on that)
Cover
Write the word, saying the sounds as each one is written
Check by sounding out and blending the word exactly as written (not what the child thinks he has written)
Visual check if needed
If you want to use ICT text to speech programmes are quite easy to obtain nowadays and are brilliant for emphasising the relation between letters and the sounds they spell as they will read back exactly what has been written. You do have to use one with a British 'voice' as US voiced ones will 'read' the words with a US accent; not helpful...
I appreciate that some children still find it difficult to remember the correct spelling for a particular sound if there are a number of alternatives, but phonetic spellings are a big improvement on collections of letters in random order.