When you draw blood, don't go for what you see, go for what you can feel. I know this sounds like a karate lesson, but close your eyes and feel for one. You know where they are supposed to be and you can see them sometimes. But, if you can't feel it, don't try it unless it is the last resort. I would rather use butterflies, but they hurt much more than other types. I don't have that much experience in elderly sticks, except for my mom. I have to stick my mom and send the blood to her doctor. I use a butterfly and I draw from the veins in her hand. The other options are not good choices because I can't feel or see anything. I feel like I am in control better with the butterfly.
With the needle and tube holder, I had trouble at first because I introduced the needle as if starting an IV rather than a blood draw. Remember to go at an angle greater than the angel for IV insertion. As soon as you see the blood coming into the tube, release the tourniquet, take the tube from the holder and quickly remove needle, apply pressure, and dispose of needle. Well, dispose of the needle safely and as soon as feasible. Like the post before me, do not bend the arm if you use the site mentioned before. I have had to practice many times, and I still have bad days. If you can, make sure you're patient has had fluids. If you can, warm the sight you're going to stick. Make sure the tourniquet is tight. Have the patient make a fist or hang his arm/hand below the level of his heart.
When all else fails, look at the thumb. I've had to infuse fluids through an IV I started in a thumb. No other choices. No one to turn to for help.
Practice and time. It will be second nature to you soon.