Nail art pens(cost a dollar or so,easily available)
They have a nozzle on one end and a brush on the other.
They can be used both ways.nozzle is a little thicker compared to the brush but useful if design doesn't require detailing.brush is best for small detailed designs.
Brush can be used as a regular brush to draw and nozzle is used to fill in the designs.i use a pin to create very fine details.toothpick or pen tip can be used for the same
These can be very easily made if you are used to colouring or drawing. Use the brush for easy lines and nozzle to fill in the colour. Use a pin or toothpick for details. Each hand takes about 10 min.