Tool - Pocket Hole Jig
Kreg Mini
Manual: https://www.kregtool.com/webres/Files/mkjkit-product-manual.pdf
Set it back 1-1/4" for drilling 1.5" material (2-by)
Set collar 4-1/4" from big drill shoulder for 1.5" material (2-by)
Use 2.5" screw for 1.5" material (2-by)
You will need to make yourself a jig from some scrap 2x6 lumber to hold the Mini the right distance from the edge and to hold it square. Glue the Kreg Mini into a slot in the wood using PL-Premium adhesive. Don't block the sawdust exit hole. The wood makes it big enough to hang onto rather than having to bother with a clamp. Put a mark under the entrance hole to make it easy to line up with a line you draw on the wood you want to drill. Kreg minis are inexpensive enough that you can make more than one jig if needed. It's nice you get a new stepped 3/8" drill bit with each one. I also use the Kreg 3/8 drill bit for regular holes because it avoids having to drill a pilot hole.
Weather resistant screws
Kreg SML-C250B-2000 Blue-Kote Weather Resistant Pocket Hole Screws - 2 1/2", #8 Coarse, Washer Head, 2000 count .
These are nice screws and not too expensive, but they are a little thin and not suitable for doing 90 degree joints in 2x4s. You need 3" screws for 90 degree 2x4 joins.
http://smile.amazon.com/Kreg-SML-C250B-2000-Blue-Kote-Weather-Resistant/dp/B000VK3TGQ/ref=sr_1_119?s=hi&ie=UTF8&qid=1424196645&sr=1-119 $70 for 2000 3.5 cents each
Kreg R3
The holes are not the right distance apart for 2x4s.
$39.97
Instructions: https://www.kregtool.com/webres/Files/r3_manual-tri-lingual.pdf
Kreg HD
For 2x4s, when you need huge strength the Kreg HD is useful. This works with the large weather coated Kreg screws. You clamp it to the end of the 2x4 and drill the holes. The drill bit is larger (1/2") than the standard Kreg drill bit. The biggest issue with the HD jig are that the big screws are expensive (17 cents each!). The drill bit is useful for drilling regular 1/2" holes because you don't need to drill a pilot hole.
http://www.homedepot.com/p/Kreg-Jig-HD-Pocket-Hole-Jig-KJHD/204614706
https://www.kregtool.com/store/c13/kreg-jigsreg/p59/kreg-jigreg-hd/
Big weatherproof screws...
http://www.coastaltool.com/a/ab/kreg/hdscrews.html?mv_action=refresh&mv_order_item=KREGSMLC2X250125&id=ifqWwLNT#cart 125 for $12 + 8.50 ship
Kreg K5
For benchtop work, a Kreg K5 Pocket-Hole Jig is useful. You can use the Kreg HD jig as an insert for the K5 benchtop system. The main issue is that it is expensive. I prefer to just use Kreg Minis in my own wooden jig.
http://www.amazon.com/Kreg-K5-Pocket-Hole-Jig/dp/B00EF3L9BM $139