Of course it always helps when circulation is increased to the hair roots BUT if you use the wrong type of brush, brush too much or brush improperly, it can actually cause teeny tiny hairline cuts to the scalp which can have a damaging impact and actually in some cases cause the scalp to react and hair to be shed.  

In reality, hair brushing should be limited to detangling and limited styling.  The idea that 100 strokes a day will help hair and scalp is an old wives tale.  In most cases it will do more harm than good. 

Brush Types To Avoid

Brushes which are bad for hair and scalp (causing breakage and tiny cuts to the scalp) include the following:

• Brushes with knobs on the ends that will rip and tear follicles
• Brushes with heavy synthetic brush
• Plastic brushes
• Brushes with sharp teeth or sharp edges

Best brushes

The best hair brushes are made with 100% all natural boar's bristle or a high quality synthetic boar's bristle that are soft and without knobs on the ends.  If the brush feels soft on the skin on your arms, it will be soft for your scalp.  Mason Pearson and Kent make the best 100% boar's bristle but Conair has some wonderful high quality synthetic versions that are also good for hair and much less expensive.

Instead of Brushing Consider Scalp Massage Instead For Circulation

The very best way to generate circulation is to use the pads of your fingertips...making sure that your nails are well trimmed to avoid scratching the scalp...and then start with gentle, small circular movements on the scalp working from front to back of the head.  It is also good to use a tiny bit of warm jojoba oil applied to your fingertips to massage into the scalp. 

Never use more than a tiny bit of oil though because too much oil can sometimes cause long range follicle clogging problems.  A little bit is fine and jojoba, which can be purchased at any health food store, is an excellent oil to use for the hair and scalp.

For more info on jojoba oil check out:
http://www.hairboutique.com/tips/tip10044.htm - http://www.hairboutique.com/tips/tip10044.htm

If you are unsure about how to massage....any good massage book will give you good basic step-by-step instructions.