The eco flow water based you can dilute with water. I have never used them though. I started out with fiebings and haven't seen a need to switch. Fiebings should always be used with good ventilation. You can also were a respirator for that.
Most people shoot for a 50/50 mix to begin with and apply more coats to darken. I have always found 50/50 to be too dark for my tastes so I usually start at a 3 to 1 or 5 to 1 ratio.
I either dip them or apply with dollar store sponges cut into thirds.
If applying with a dauber or sponges make sure and get even coverage.
Start across the piece going one direction. Then perpendicular, then diagonal. This will help even out the application. However, it will get dark quick. Hence the higher dilution ratio I use.
For the fiebings spirit dyes people either dilute it with a solution from fiebings or denatured/isobuterol alcohol.
I had been using featured alcohol, but decided to try plain old filtered tap water. It worked like a charm and I haven't looked back.
The more you do this, the more of your own techniques will develop. As time goes on you will probably just dismiss me as some guy rambling on the internet who thinks he knows what he's talking about.
Keep having fun.