Go to Joannes fabrics or Michaels or comperable craft store look for American Painter Brushes.
They are the ones with the dull grey colored handle are the best & most reasonable priced.
I use 10/0 & 6/0 liners for most everything.
If you do a lot of blending you might profit from a thicker liner.
These brushes need inspection before purchase, be sure they are of the best possible quality when compared to one another.
I actually run the bristles through my lips ( with a tad of saliva * I know what yer thinkin* ) dont worry your the only wierdo doing it unless you have the misfortune of living near me
If the bristles dont line up to point = dont buy
If they have extra long bristles extending from the rest = dont buy
If you find one that meets the above criteria run it back & forth test for any rouge hairs / broken hairs ( been bent too long , wont go back )
These brushes will need a bit of breaking in, use them to fill spots after priming a mini with watered down paints.
When they are used will give you amazing blending & straight line potential.
They will also start to hook this will give you the ability to make lines, dots, reach details with accuracy ( like curved tip dentists tools )
Give em a shot they are super cheap easy to find.
TH