I use a blood knot to connect my leader and tippet. There are a couple things that help me and my middle age (61) eyes.
Start with a good amount of leader and tippet to work with to make your knot. It makes the job simpler.
Picture the leader in your right hand and the tippet in your left hand. I use a good amount of tippet and line to do the twisting. I place the leader behind the tippet and wrap it first. I wrap or pass it over the top of the tippet. Pinch it with your thumb and first finger of you left hand and pass it to your middle finger and ringer on your right hand. You are pinching between your middle finger and ringer when you take it from your left hand. Passing from the end that you are wrapping from one hand to the other is what made tying a blood knot easy for me. Again, starting with a good amount of leader and tippet helps you do this.
Also, when you wrap the second portion leave a large space to insert the leader into the hole. It really helps if you have middle age eyes.
For me learning to tie a blood knot was like learning to do a whip finish. There were no tools at the time (1971). To a certain extent I think the blood knot tool makes it more difficult.
Reading these tips on knot tying is not the same as watching someone do it. If my "tips" didn't help just post the grumpy, red smilie and I will understand.