i agree with most above. Dont waste your time with ordering flux or silver if your supplier doesnt have them (one of the reasons i order true temper for HJ is i can get great consumables *hint for nova*), and 45% will have plenty of strength for these apps, and the gap filling may just come in handy for you as a beginner. Bottle bosses are easy, but after i gave the tinning a try, for guides and such, i wont go back. for this you tin (a little peak of about 1/32nd thick of filler is nice here), then tin your boss, clamped in some needle nose. reflux if you feel like it, place it where its gotta go, heat up, and watch the marriage occur with a steady hand for about 5 seconds after the melt and flame has been removed. Ive pissed around with boss clamps far too much, and for many apps this is a great tech. Personally i think practicing with silver for boss' is a waste. If the metal gets orange with a micro torch and you havent had a good flow occur, you have filler or cleaning problems, no biggie, clean again (sanding is one of the best cleaning agents out there, make sure it is sanded nice and bare first, and then if you like, acetone is nice with silver i find, or some snobol, and go at it. using a 2500f flame on silver will give you a huge window...keep the flame dancing around at all costs still. The hardest part here is getting those bottle boss' center on the tube, 1/16th of an in never looks so drastic as it does on them. anyways, im done rambling. have fun.