Lets look at the brushes which are available:-
Ideally the softer the brush the less the damage to the paper, therefore a brush containing sable, hair, squirrel will be ideal. The size will depend on the area of wash to be applied.
The next question is size and shape:-
Examples of brushes.
1: Pure sable
2: Mop with Squirrel
3: Flat Synthetic
4: Goats Hair
5: Hake
I have indicated elsewhere the brushes which I would advise initially but you may wish to look at these since they can all have their uses and given resources you may like them in your painting box.
Palette: What is available:-
The biggest error with all painters is running out of paint before the wash is completed. First it is rarely possible to mix the same colour and by the time one has the first part of the wash has dried and back washes occur.
A flat palette containing at least 7 areas for squeezing paint into from the tubes is useful and is what I recommend for beginners to my course however, I particularly like this type of palette or something similarly as deep when applying washes, or painting subjects where I know I am going to need some strong paint dropped into an area of wash. Paint is squeezed from the tube onto the top and the dishes used for mixing the weak washes.