You first thing should be to get the larger lumps of fluff out.
If you simply blow it, you will probably get a mouthful of crap as the dust flies about, counterintuitively this is because when you blow you create a fast airflow but also a low pressure zone, similar to a ventuari effect. Result is that the dust goes into your mouth.
You can buy small cans of compressed air instead, but first I would simply use a vacuum cleaner but make sure to keep it clear of the item, do not touch it with the nozzle or you risk damage.
Next job, get yourself a small paint brush, and very gently brush the muck out, you want to blow any loosened stuff away.
I tend to then use a 1inch brush with shortened bristles to gently scour the board, shortening the bristles makes them less bendy.
I put the brush on one spot and just wriggle it around on that one location, I do not sweep it or drag it about.
You have to be really careful though, if you feel any components have some movement or play in them, its best not to do this or you risk damaging soldered joints.
Use of solvents is a difficult one, the main worry is that something too agressive will at the very least remove compnent markings, or could seriously damage variable resistors etc.
Other solvents leave a film behind which then attracts dust again.
Even mild solvents on old components can cause damage.
Its very slow, but cotton buds are your friend.
When you do resort to cleaing, a word of advice, make sure the item works first, clean a small patch, test it again, its lengthy but if it suddenly stops working you will know the area to look, and the chances are that a connection has been distrubed.
If you do it all at once and it doesn't work, you won't know hwere to start.