I do all of my brother's speech therapy at home with him. We have an ST who we see once a month and she works with him, gives us more exercises/ideas to do with him. We've always been like this - doing everything we can for him when it comes to my brother's therapies. I've educated myself on ST & OMT/OPT (oral motor therapy aka oral placement therapy) and do a bunch of exercises with him every day.
When it comes to speech therapy or oral motor therapy the key is persistence. If you are not persistent, your work will take much longer to pay off. We've already seen our work paying off and it is so great!
The main area my brother needs work on is his jaw. Jaw stability is key to success in speech. The jaw is the fundamental support of all components of speech. Then comes the tongue and lips. Of course we are also working on his tongue and lips, but tongue retraction will come when there is proper jaw strength. If you work on the lips & tongue first, yet don't have proper jaw strength & stability, you are not going to get very far.
Bite Blocks are essential for building jaw strength. When I first tried the Bite Blocks with my brother, he would not bite down on them *at all*. This is due to a few reasons, but in particular, lack of jaw strength. So, we went to having him chew various foods on coffee straws, since that would help his jaw. It would also help him realize that he needed to bite and it would make him do the chewing motion. I would put a small piece of food on each end of the straw (either a fruit chew or cheeto). One end of the straw would go in my mouth on my molars and the other end in O's mouth. He would see me chewing the straw/piece of food and therefore he would want to do it to be able to do what I was doing. We had great success with this and he was able to work up to 12-15 repetitions a day.