Agar powder in mousse

I've tried this several times and I've run into problems each time at the same step. I dissolve the agar in a hot liquid (or warm), but when the dissolved agar hits the cold ingredients it immediately seizes up and my mousse (and lemon curd) gets weird little bits in it. I strain them out, but then I am essentially straining out all the agar I just used to give body to my mousse.