I took on a couple rough Parkers that have been completely dismantled, one of which is back in service. I am not a gunsmith. I asked the same question a couple years back and got a few recommendations. I decided to go with the Brownells sets.
I found that these sets will have a tip that fits (except for the unhooking pin screw. That screw slot is so small, I found what I needed in a set of jeweller's screw drivers). I did not have to grind any of the Brownells tips. You definitely need the "thin set" as well as the "super set".
The goal is to completely fill the screw slot side to side, depth and full width. So, the very first thing to do is clean the slot of debris, rust, dried hard oil or whatever else might be in there. Toothpicks are a good start but if you need something more aggressive a dental pick can be used. Once the slot is clear of foreign matter, you need to find the tip that best fits the slot. You can succeed if the width of the slot is not completely filled (but almost is). Depth and side to side of the slot are critical to be filled by the tip, otherwise there is a good chance of burring the screw head. This is why the wood shop or mechanic's screw drivers with wedge tips should never be used on your Parker screws. You might get away with it but the risk of damage is high. One screw that is often seen damaged is the "joint pin screw". Unless there is a very good reason to remove this screw, like a severely damaged "joint roll", it is probably best to leave it alone. I've started to believe that all those damaged "joint pin screws" out there are due to someone thinking they would take the gun apart without knowing what that screw does. It is a big screw and looks like it should be an easy removal but it is not. Torque transmitted by hand is usually insufficient. The more one applies increasing torque to no avail, the greater the probability of slipping and damaging the head.
With proper driver tips, patience and perseverance and maybe some penetrating oil if needed, non gunsmiths can dismantle, clean and re-assemble their Parkers. You will also need a small hammer, drift punches (brass or nylon preferred over steel) and six inches of 1/4" dowel.
Here are two links. If you decide to DIY, don't scrimp on the driver sets. Your Parker will thank you in the field or at the range. No commission from Brownells but I'm happy with mine.
Jack
Magna tip super set
http://www.brownells.com/.aspx/pid=4...ER_SETS_trade_
Magna tip Thin Set
http://www.brownells.com/1/1/3693-ma...brownells.html