I use the cheapest, blond wood-handled variety from any hardware store.

Trick is - after you've pulled a new brush's bristles through your fingers, stripping out as many of the loose bristles as you can manage - take a pair of scissors to cut about 1/4 to 1/3 of their length off, leaving either a straight edge or a slight curve which I found works better.

You can still use denatured alcohol or xylene (solvent) to clean 'em for re-use if you wish but more often I just toss 'em out.

Great question.....i think about it more in terms of the total procedure i am trying to perform and why am i using a brush (or do i even need one) and which is best for the purpose.

so for example, if i am wetting out the cloth on the outside of a hull, my main tool is going to be a spreader to move epoxy around and i will use a two inch foam brush to to touch things up and maybe apply some additional epoxy into a place that i can't get to with a spreader.   

if i am applying a fill coat, the main way i am going to move epoxy around is with an epoxy resistent foam roller...and then a foam brush to brush out the bubbles.

if i have a complex part with concavities, i use a bristle brush to get the epoxy where it needs to go.

generally, the foam brush will start to break up if you are trying to actually soak it with epoxy over any elongated period of time...hence i use them for tasks like bubble smoothing or a short tactical application of epoxy that i can't do with a spreader.

i use bristle brushes when i need to really deliver epoxy or move cloth around aggesively in a location that due to its shape, just doesn't work well with a spreader.  a great example is the most curvaceous/complex shapes of the inside of the deck around the coaming.  the only problem with a bristle brush is potentially losing some bristles...but a little ca glue at the base quickly addresses that problem....but i usually just use them out of the box and pull a bit on them to get rid of any obviously loose ones.

at the end of the day, i never try to save any brush. 

anyway, my standard aresenal for building a kayak is a box of foam rollers, a box of two inch foam brushes and a box of two inch bristle brushes and a spreader set.  the spreaders i do clean up and reuse so one pack will easily do a kayak.

i hope that helps.

h

   Hmm great idea in cutting it,  I do end up with bristles in the epoxy too.  I might give bristle brush another try with those recommendations.  I've found the epoxy foam rollers CLC sells to be great, the "thin nap yellow" ones.  If I use those and tip out with a foam brush I get a pretty nice result.  The issue is the corners, concaves, etc.  I was getting too many drips with the bristle but get a nice results with the foam brush.  The biggest issue is the foam brush leaving presents in the epoxy.  They fall apart so fast.  I toss em,  but my time is limited with a 2 month old and 2 year old so spending all my time cleaning up foam bits is not ideal.  I redid the skerry interior this week to ensure I have a thick enough coat but ended up with too much foam around the inwale blocks and such.  Oh well,  more sanding fun to clean up what I missed. 

Thanks for your input!  Inwales go on soon, excited to be working on it again.  The birth of our second born slowed things down a bit :)

 If you have a Harbor Freight store near they have a box of 50 2" chip brush for cheap, like hspira said pull out the loose fibers and cut 1/4 to 1/2" of the end. My wife will use one to baste melted  butter on homemade rolls and bread.   

Don't infer my suggestion about cleaning cheap brushes as a directive, that's not how I intended it. But you can rinse them free of epoxy (mostly) if you choose to, especially if you've carefully trimmed one to a specific shape that you then want to save for re-use later.

I find a plastic blade spreader most efficient for surfaces that are close to flat, otherwise it's a roller that gets grabbed. Cheap, trimmed 'chip' brushes are for doing stuff in tight areas or where you want precision placement such as when putting a priming layer down before adding thickened mix for bonding, or running fillets.