From leeneia's opening post:

This time I bought a new type - a chocolate brown one with gold writing that says National.

Those National thumbpicks are nothing new to me ~ they've been my favorites for decades. When I started playing more frequently a few years ago, after a long period of relative inactivity, I eventually lost my thumbpick and had difficulty finding a new National to buy. Most music stores hereabouts didn't even carry thumbpicks and fingerpicks, only flatpicks. Where thumb/fingerpicks were available at all, the selection was always limited and inadequate. I spent about a year buying and trying various bogus thumbpicks before finally locating a source for the quality National product that I needed.

National thumbpicks come in sizes; mine says "National M" (for medium). Is yours, perhaps, an "S"? One's preference is dictated not only by the actual size of the thumb, but also by how tight a fit one prefers.

Unlike flatpickers, who use, lose, and discard their picks quickly and often buy them in quantity, fingerpickers tend to keep a single set of picks, or maybe two, and may go for years without needing to buy replacements. This is not so much because of the thumbpick, but the fingerpick(s) ~ at least, for those of us using metal ones. Custom-fitting a couple of picks to STAY on your righthand fingertips can take a while, and once you get 'em right, you really want to keep track of your set of picks and not have to start the fitting process over again with new ones. (National is a leading source for the best metal fingerpicks, too.)

I have to disagree with Kaleea that it's necessary to strum over the soundhole. That position does yield an excellent all-purpose sound, but I deliberately move above and below the soundhole to achieve a wider variety of sounds; picking/strumming closer to the bridge provides an extra-bright "ringing" sound wherein each string is individually audible, while moving up towards the fingerboard makes for a softer sound that emphasizes the harmonic sound of the chord as opposed to the notes of which the chord is composed.

That's on a guitar, now; I can't speak for the dulcimer and other instruments. But how much different can it be?