I've found the Fender B-29 to have reasonable volume acoustically. If your budget can handle a bit more, don't make any decision without trying the Tacoma acoustic bass guitar (gonna just refer to'em as ABGs, from now on).

As far as volume itself is concerned, you really should consider playing with a pick. If you don't like the hard sound a regular pick can produce, try to find one of the hard felt picks like the archtop swing and jazz players use.

Re: electrics in sessions - I've gotten appalled looks (usually in mock jest) when I've walked in with an electric & an amp. When it becomes evident after a couple of numbers that I understand that the volume knob can work in a counterclockwise direction, I seem to have no further problem with acceptance.

Also, if there's more than one bassist at a session, taking turns is probably a good idea.

Last thing: boiling strings - yech! I tried it; it does freshen them, but I don't think it lasts long enough to be worth the travail. Unless you're very broke (bass strings running from $30 - 50 (Cdn) a set).
The recipe: take an old pot that will NEVER again be used for food prep. Fill with water and a cup of vinegar. Boil for 20 minutes or so. There ya go!