First, the serious stuff---bow hair is made of horses tail hair ( hopefully, and not fiberglass, if that is the case, let 'em lick it!) and hair has scales that run one way, just like snake scales. When you rosin the bow, it picks it up going one way, and smoothes it out going the other. On fresh, or clean hair the scales are lying down too smoothly to pick up rosin,(which actually does nothing except create friction), so you have to rough up the scales by getting rosin on them. As Malcolm says, scrape the rosin cake to get some powdered rosin first as it adheres better than the stuff right off the cake.
'Spaw----yes, frogs are dehydrated, and yes, Malcolm, my animals have brought me dehydrated toad/frogs, but for real, the frog is wood, and the screw/other parts are metal-the wood will swell, and the metal will rust. (Are dehydrated Budwiser frogs fit to drink?)
Crowhugger---if you still have plenty of hair in your bow, you do not need to re hair. I don't know what the preferred number of hairs in a cello bow is, with violin, it is somewhere around 100, give or take according to the bow. If it does not look de-nuded or thin, give it a wash and a re rosin and see what happens. It's free, and you can always have th bow re-haired for $$.
As far as the beginner/good vs junk goes, this is true up to a point-----just where the point is, is the question. Should we buy our 2 year old beginners genuine Strads, just because we have the bucks? No, they will ruin the instrument. Just like any other instrument opt for maximum setup,& strings on the cheapest instrument your EAR likes...........and spend the extra money on a good bow. It is amazing how much difference a good bow will make, and bows often sell for more than the violin itself!
Actually, I really like 'spaw's suggestion of buying a cheapo bow and spray painting stripes across it. It would be more visually attractive, and you would not have to worry about your good bow.....

OK Guys!!! What is this about frogs?? Everybody knows that the best selling beer in Ireland today is .........you guessed it, Budweiser. So, get yourselvesFroggiScreen Saver and bite a worm........(Mbo, Fire on the Mountain is better than O.B.S.!!)

We already have Potty Pickin', Breasts, Monkey Farts, and Austria; let's not get started on screws! Pleeeeze?