How to improve as much over the summer as possible with no teacher but a lot of time?
Unfortunately, I’m in a sticky situation with a lot of time to practice but no chance of a teacher. However, I really want to use my time to really improve. Right now, I’m pretty intermediate and can play Roumanian folk dances and Kabalevsky. How would you structure 2-3 hrs per day to be as efficient as possible? I’m thinking Kreutzer and Sevcik double stops, trills, and bowing. I'll definitely work on my practice habits by keeping a journal and recording myself.
One thing I did, between teachers; acquire a copy of Flesch Violin Fingering, put it on the stand, plow through. And there are more technical books like that by, Ricci, Szigeti,..
Do lots of listening to recordings to get some help with interpretation, and do lots of recording yourself so you can pinpoint areas that you can work on. Also spend this time polishing weak areas of your technique whatever it takes. You can also start looking at new pieces that your teacher says you can learn.
Deliberate practice. Identify your weaknesses, and work so they become strengths.
What has always worked for me has been to have a specific goal. For example select a piece of music you want to be able to play (hopefully at performance level) by the end of the summer and go to work on it. Look at the parts you cannot handle now, break them down into study portions, look for etudes/exercises that emphasize the needed technique improvements and use them in your daily warm-ups.
Recording yourself is a must. Developing a critical ear and the ability to be self-critical requires reference points.
Some amateurish suggestions.....
If you're not sure what technical aspect of playing to work on, record yourself playing, preferably on video, and pick something you're not happy with. I do that daily, and often choose exercises or etudes to work on based on what I've been dissatisfied with in recent practice sessions. Sometimes, I've spent a month or two working on one thing if it needs serious remediation. (For example: bowing exercises every day for the whole summer in 2016.)
Make Schradiek school of violin technique vol. 1 part of your daily practice.