Hydraulic lifters have a spring inside of them that keep the plunger fully extended when no load is placed on the plunger, i.e. when the valvetrain is not installed. If you have the head off the engine, it is a perfect time to degree the cam and measure the specs of the cam since you can put the dial gauge on the deck of the engine block and read the camshaft movement directly off the lifter. The lifter will not need to be pressurized since the only force on the plunge will be the dial gauge.

Yiou need to find out the cam profile before you start advancing or retarding the cam in relation to the crank. The "advance it four degrees" works on stock cams, and in general advancing a cam improves low end torque, but you need to know what you are working with before you start deciding how much you are going to change the cam timing. This is especially important if you are trying to achieve a certain dynamic compression ratio.

Once you get it all back tegether and want to check compression, you should be able to check the compression by cranking the engine until the oil pressure light goes out on the dash or until you start seeing oil coming out of the rockers on the head. Hydraulic lifters only need 3-4 PSI of oil pressure to "pump up," and this is easily achieved by cranking the engine over with the starter for a little bit. Just make sure the fuel line is detached form the fuel pump so you don't pump gas everywhere.