re. "Difficult to use only the rear since you can only hold up on the left side."
Keeping a foot on the rear brake after a stop may look cook but it's a lot safer to bring the bike to a complete stop and put both feet down. No reason to keep your right foot on the brake after you stop since the front brake is the safest to use then. The only time I do that is if I have to stop on the downside of an incline, since I'll need my right hand for throttle to make sure I don't stall. No fun stalling on an incline, especially if you have to make a turn.
Hey Pedro, if you are going to ride anyway despite our warnings:
Keep your head up in a slow turn and look to where you want the bike to go. If you look at the center line or the oncoming car your bike will go towards them, the more you panic, the worse it will be.
In slow turns keep your foot lightly on the rear brake while feathering rpms to about 1100. The revs of the engine act like a gyroscope and will keep your bike up. And you can turn so sharply that you can scrape your floorboards. (Don't try that yet OK?) HEAD UP!! Don't look down at your tire or the road right in front of your bike.
If making a sharp turn snap your head and look directly down the street, or over your shoulder if you have to make a u-turn.
Always scan the road surface for sand or gravel before the turn (you prolly know this already)
If you hit your front brake firmly in a slow turn you are going down.
Countersteering: If you press downward on the right handlebar the bike will sway (turn) to the right. Same for left. This works anytime you are going above about 5-10 mph. Slower speeds require you to physically turn the bars but countersteer can still be used to contribute to turns even at slow speeds.
Practice in a parking lot, not the road. Once you feel comfortable, keep practicing.
Here's a cool link to how it's done. You will learn a lot from this video. Keep your eye on his right foot and brake lights and notice how he NEVER touches the front brake. Also notice how he looks far ahead to his target and only glances down to the cones occasionally. You can hear him scraping off our taxpayer paid for floorboards on every turn.