You should thin oil based paints with paint thinner, not lacquer thinner. Lacquer thinner is what you would use if you are using lacquer based products. I am not familiar with DIY versions of airless sprayers, but I'm sure that would be better than the HVLP. You should never need to thin anything. You will notice a lot more overspray with a rig like that though.

megnliz, the Magnum X5 is a DIY airless for occasional use. Any pro airless is going to start at around $700 like the Tiran 440i. The difference is in GPM, durability and repair-ability and nicer gun. These features are very important to painters, not so much to DIYs. Not that the X5 won't suffice to your needs; it's probably a good value for your use.

Now, I have used oil Coverstain with a compressor driven HVLP for kitchen cabinets and yes, I did reduce it with mineral spirits (paint thinner). Don't use lacquer thinner.

The main disadvantage to large airless is that clean up is cumbersome, so you don't want to break it out unless you are spraying large projects.

Another option is a handheld airless like the Graco Proshot. You can shoot straight from the can since they pressurize to like 2,000 psi. There are several models, but again they are meant for smaller projects.

Lastly, have you considered renting an airless? you get to use a pro model and return it after you are done. You can probably set up and prep all your large projects and finish in one day.

I hope this helps.

The clean up of the large machines is not only cumbersome, it requires a lot of paint thinner to purge the machine and all its hose. This is especially bothersome if your project must be done over several days.

The handheld Gracos are nice because of the rapid clean-up: pour out the paint, rinse the container, and spray a little paint thinner. Home Depot has the Graco 360 DSP for well under $200. It is unique in that having no pick-up tube, it can literally sprayed upside down.. The throw away plastic container can, indeed be thrown away or, cleaned and reused a few times.

Were I to spray the whole house in a short time, I would probably just rent a larger machine. Get all your prep and masking done before renting the machine, so it is "blow and go" on spray day.

I have the Graco TrueCoast 360 VSP. It's a handheld sprayer. I just tried to shoot Zinsser CoverStain (oil-based primer product # 3551 (check there are different product #s)) with very poor results. There were pulsation marks, tails and the dried finish was like orange peel. The primer is thick. I double checked tip size requiremnets. The sprayer uses 0.015 tips and the paint requires 0.015-0.017 tips. The problem was likely the pressure. The paint needs 1800-2200psi and the Graco can only output 1500psi. I thought I checked the pressure compatibility, but must have gotten it wrong. The paint says DO NOT THIN. I've read a few reports, one above included, where it was thinned with paint thinner. I don't know how that will impact the paint. In my case, I don't need a stain blocker, just something to bond to clean maple kitchen cabinets so the top coat with stick properly.

I'm going to try to thin the primer and shoot again with the Graco VSP and test how well it sticks, although I'm unsure how well it will hold up overt time if thinned. I also have a Wagner PaintCrew (its old) that run at 2800psi and can use 0.015 tips that I'll try. Clean-up is a real pain and uses lots of mineral spirit.