Try Jolly Phonics. The workbooks are really fun for children to work through. You don't need all the Jolly Phonics "kit"just the workbooks and flashcards are enough for practice. You can also snip up the last page of the workbook and use the words as mini flashcards. You can also make your own CVC flashcards with cardboard and a penjam, tip, lid, sip, mat, fan, etc.
Do sounds, not letters, and don't add "uh" sounds after the sounds. S should be a hissing sound, not "suh." F should be a puff of air, not "fuh." The voiced consonants like b and g are impossible to say without adding a small uh sound, but try to keep the sound as short as possible.
Do not teach letter names or waste time drilling them on the order or singing the ABC song. Stick to lower case letters for the moment, following the pen strokes suggested in the workbook, and stay away from capital letters for the moment. If you introduce caps and lower case together, they end up sticking random caps in half their words and you waste time and energy trying to correct the habit.
Have fun and do just a tiny bit at a time!