You can buy plastic containers from any good paint places. I got some 1ltr ones from memory. They have measurements and ratios printed on the sides - and lids.

These make life much easier and cleaner. Plus, I always give the paint a good stir before putting in the gun to make sure the thinners are mixed well.

When doing the roof, I found with a gravity fed gun, don't put too much paint in, as it can spill out the top cap / reg. Much easier to have the containers here for a quick top up! (I only mixed 1ltr at a time).

I'd say you need to buy more thinners too - 1:1 + plus primer + cleanup.

I didn't wear gloves, but I'd probs at least get some washing up ones etc, as long as the thinners doesn't eat them. Paint + thinners + skin doesn't mix well - also the extra getting into your blood.