A half mask is not good enough. It doesn't protect your eyes. Forget those. Get either a full face mask or a hood. Also get a system that utilizes a continuous air flow. I use a full face mask. If you need to wear glasses when spraying, a hood is perhaps the better choice. One thing to remember if you use a full mask and wear a beard: Make sure your air supply is sufficient to maintain a positive pressure inside the mask when you breathe in. You can check this by breathing in deep and rapidly while assuring there is still an outflow of air at the mask exhaust port, using your hand. An air supply should be a minimum of 4 cfm for a full face mask and 6 cfm for a hood and should not come from a lubricated compressor.
I use a dedicated, 1 hp, non-lubricated air compressor to supply air to my mask. I like being able to utilize a regular 3/8" air line to supply the air to the mask. Makes it a little easier to move around than having a larger hose typical of the low pressure blower type systems.
Yes, you still need a fresh air system when spraying outside. You also need to make sure that your source of breathing air is located where there is no possibility of ingesting contaminated air of any kind.